Process for producing poly(ethylene-aromatic dicarboxylate ester) resin and resin product

ABSTRACT

A poly(ethylene aromatic dicarboxylate ester) resin usable for the production of fibers, films and bottle-formed articles, is produced by polycondensing a diester of an aromatic dicarboxylic acid with ethylene glycol by using a catalyst including a non-reacted mixture or reaction product of a titanium compound component including at least one member selected from titanium alkoxides and reaction products of the titanium alkoxides with aromatic polyvalent carboxylic acids or anhydrides thereof, with a specific phosphorus compound, in which catalyst the contents of titanium and phosphorus elements are controlled.

TECHNICAL FIELD

The present invention relates to a process for producing a poly(ethylenearomatic carboxylate ester) resin using a polycondensation catalystobtained from a titanium compound and a phosphorus compound, the resinobtained by the process, and products thereof. More specifically, thepresent invention relates to a process for producing a poly(ethylenearomatic carboxylate ester) resin, which has excellent transparency,excellent color tone and excellent melt stability, without formingforeign matters (or with forming less foreign matters) originating froma polycondensation catalyst in the production process using apolycondensation catalyst obtained from a titanium compound and aphosphorus compound, a resin obtained thereby, and formed productsthereof, for example, fibers, film and bottle-formed article.

BACKGROUND ART

Poly(ethylene aromatic carboxylate ester) resins such as polyethyleneterephthalate, polyethylene naphthalate, polytrimethylene terephthalateand polytetramethylene terephthalate (which will be referred to aspolyester resins hereinafter) have excellent mechanical properties,excellent heat resistance, excellent electric insulating properties andexcellent chemical resistance and are widely used as materials forforming shaped articles such as fibers and bottle-formed articles inwhich the above-mentioned properties are utilized.

As the process for producing polyethylene terephthalate, for example,there is known a process of directly esterifying terephthalic acid withethylene glycol, or transesterifying a lower alkylester of terephthalicacid, such as dimethyl terephthalate with ethylene glycol, or reactingterephthalic acid with ethylene oxide to form an ethylene glycol esterof terephthalic acid and/or a polymer having a low polymerization degreeand polycondensing the reaction product with heating under reducedpressure until a predetermined polymerization degree is attained.

In the production of the polyester resin such as polyethyleneterephthalate, generally a polycondensation catalyst is used in order toallow the polymerization reaction to smoothly proceed. The rate of thepolycondensation reaction and the quality of the resulting polymer aredrastically influenced according to the kind of the polycondensationcatalyst. Various metal compounds are known as the polycondensationcatalyst. Among these metal compounds, an antimony (Sb) compound such asantimony trioxide is widely used because it is cheap and has a highpolymerization activity and also the resulting polymer has comparativelygood color tone. However, when the Sb compound is used as thepolymerization catalyst, a portion thereof is reduced during thepolycondensation reaction to form metallic Sb or other foreign matters,and thus causing a problem in that the resulting polymer is darkenedand/or the production process is made unstable, resulting indeterioration of the quality of the formed article produced from theresulting resin.

When the Sb compound is used as a polycondensation catalyst forpolyester and the resulting polyester resin is continuously melt-spunfor a long time, foreign matters (which may be referred to as spinneretforeign matters, hereinafter) are deposited and accumulated aroundspinning orifices and a bending phenomenon arises in molten polymerstreams, and thus causing a problem in that the filaments are fuzzedand/or filament yarn breakages occur in the resulting filament yarnduring the spinning and drawing steps.

As the polycondensation catalyst other than the antimony compound, agermanium compound and a titanium compound such astetra-n-butoxytitanium are proposed. The germanium compound isconsiderably expensive and, therefore, there is a problem that a cost inthe production of the polyester becomes higher. When using the titaniumcompound as the polycondensation catalyst, a phenomenon of thedeposition of foreign matters around spinning orifices is suppressedduring the melt spinning of the resulting polyester resin. However, inthis case, there arises such a known problem peculiar to the titaniumcompound that the resulting polyester itself is colored yellow and/orthe melt of the resulting polyester resin has poor thermal stability.

To solve the coloration problem of the polyester resin, which originatesfrom the polymerization catalyst, yellowish coloration is generallysuppressed by adding a cobalt compound to the polyester. Although thecolor tone (color value b) of the polyester can be certainly improved bythe addition of the cobalt compound, there arises a known problem thatthe melt thermal stability of the polyester is further lowered by theaddition of the cobalt compound, and thus accelerating the decompositionof the polymer.

Japanese Examined Patent Publication (Kokoku) No. 48-2229 disclosestitanium hydroxide as the other titanium compound used in thepolycondensation catalyst of the polyester resin, while JapaneseExamined Patent Publication (Kokoku) No. 47-26597 discloses to useα-titanic acid as a catalyst for production of a polyester. However, inthe former method, titanium hydroxide is not easily powderized, while inthe later method, α-titanic acid is easily changed in properties, and,therefore, it is not easy to store and handle. Therefore, theseprocesses are not suited for use in an industrial field and it is alsodifficult to obtain a good color tone (color value b).

Furthermore, Japanese Examined Patent Publication (Kokoku) No. 59-46258discloses to use a product obtained by reacting a titanium compound withtrimellitic acid as a polycondensation catalyst for production of apolyester, and Japanese Unexamined Patent Publication (Kokai) No.58-38722 discloses to use a product obtained by reacting a titaniumcompound with a phosphite ester as a polycondensation catalyst forproduction of a polyester. Although the thermal stability of the melt ofthe polyester is improved to some extent by using these polymerizationcatalysts, the resulting polymer has poor color tone (color value b) andthus a further improvement in color tone (color value b) of thepolyester is required. It is an effective means to use no antimony asthe catalyst in order to suppress the deposition of spinneret foreignmatters. However, according to the process using no antimony, theresulting polyester resin and polyester resin product, particularlypolyester fibers, have unsatisfactory color tone. Therefore, it hasconventionally been difficult to put a catalyst free from antimony intopractice.

Furthermore, there is known a process of regenerating a polyester resinusing, as a raw material, an aromatic dicarboxylate ester obtained byrecovering used polyester products (for example, fibers, films andbottles), followed by washing, grinding and further depolymerization. Inthis case, it is also required to develop a process for producing aregenerated polyester having good transparency and good color tone.

DISCLOSURE OF THE INVENTION

An object of the present invention is to provide a process forefficiently producing a poly(ethylene aromatic carboxylate ester) resin,which contains impurities in a decreased amount and has excellenttransparency, high thermal stability of the melt and good color tone, apoly(ethylene aromatic carboxylate ester) resin obtained thereby, andvarious formed products obtained by using the resin.

The process of the present invention for producing a poly(ethylenearomatic carboxylate ester) resin comprises polycondensing a diester ofan aromatic dicarboxylic acid with ethylene glycol in the presence of acatalyst system,

wherein the catalyst system comprises at least one member selected fromthe group consisting of:

non-reacted mixtures and reaction products of (1) a titanium compoundcomponent comprising at least one member selected from the groupconsisting of titanium alkoxides and reaction products of titaniumalkoxides with aromatic polyvalent carboxylic acids or anhydridesthereof with (2a) a phosphorus compound component comprising at leastone member selected from the compounds represented by the generalformula (1):

wherein R¹, R² and R³ respectively and independently from each otherrepresent an alkyl group having 1 to 4 carbon atoms and X represents a—CH₂— group or a group represented by the formula (1a):

andnon-reacted mixtures of the above-mentioned titanium compound component(1) with (2b) a phosphorus compound component comprising at least onemember selected from the phosphorus compounds represented by the generalformulae (2) and (3):

wherein in the formula (2), R⁴ represents an alkyl group having 2 to 18carbon atoms or an aryl group having 6 to 20 carbon atoms, n representsan integer of 1 or 2 and when n represents 1, p represents an integer of0 or 1 and when n represents 2, p represents zero, and in the formula(3), m, ma and mb respectively and independently from each otherrepresents an integer of 1 or 2,

the catalyst system satisfying the requirements (a), (b) and (c):2≦M_(Ti)≦15  (a)1≦(M_(p)/M_(Ti))≦15  (b)10≦(M_(Ti)+M_(p))≦100  (c)in which requirements (a), (b) and (c), M_(Ti) represents a ratio of theamount in the units of milli moles of titanium element contained in thecatalyst system to the total amount in the units of moles of therepeating ethylene aromatic dicarboxylate ester units in thepoly(ethylene aromatic dicarboxylate ester), M_(p) represents a ratio ofthe amount of phosphorus element in the units of milli moles containedin the catalyst system to the total amount in the units of moles of therepeating ethylene aromatic dicarboxylate ester units in thepoly(ethylene aromatic dicarboxylate ester).

The process of the present invention for producing a poly(ethylenearomatic dicarboxylate ester) resin optionally further comprisesproducing the diester of the aromatic dicarboxylic acid with ethyleneglycol by a diesterification reaction of the aromatic dicarboxylic acidwith ethylene glycol.

The process of the present invention for producing a poly(ethylenearomatic dicarboxylate ester) resin optionally further comprisesproducing the diester of an aromatic dicarboxylic acid with ethyleneglycol by a transesterification reaction of a dialkylester of anaromatic dicarboxylic acid with ethylene glycol.

In the process of the present invention for producing a poly(ethylenearomatic dicarboxylate ester) resin, preferably, the transesterificationreaction of the dialkylester of the aromatic dicarboxylic acid withethylene glycol is carried out in the presence of at least thenon-reacted or reacted titanium compound component (1); and theresultant reaction mixture from the transesterification reaction andcontaining the diester of the aromatic dicarboxylic acid with ethyleneglycol is subjected to a polycondensation reaction in the presence of acatalyst system comprising, together with at least the non-reacted orreacted titanium compound component (1) contained in the reactionmixture, the non-reacted or reacted phosphorus compound component (2a)or the non-reacted phosphorus compound component (2b).

In the process of the present invention for producing a poly(ethylenearomatic dicarboxylate ester) resin, preferably the aromaticdicarboxylic acid is selected from terephthalic acid, isophthalic acid,naphthalene dicarboxylic acid, 5-sulphoisophthalate metal salt and5-sulphoisophthalate onium salt.

In the process of the present invention for producing a poly(ethylenearomatic dicarboxylate ester) resin, preferably the dialkylester of thearomatic dicarboxylic acid is selected from dimethyl terephthalate,dimethyl isophthalate dimethyl naphthalate, diethyl terephthalate,diethyl isophthalate and diethyl naphthalate.

In the process of the present invention for producing a poly(ethylenearomatic dicarboxylate ester) resin, the titanium alkoxides for thetitanium compound component (1) are preferably selected from thetitanium compounds represented by the general formula (4):

in which formula (4), R⁵, R⁶, R⁷ and R⁸ respectively and independentlyfrom each other represent an alkyl group having 2 to 10 carbon atoms ora phenyl group, and mc represents an integer of 1 to 4.

In the process of the present invention for producing a poly(ethylenearomatic dicarboxylate ester) resin, the aromatic polyvalent carboxylicacids for the titanium compound component (1) are preferably selectedfrom the compounds represented by the general formula (5):

in which formula (5), na represents an integer of 2 to 4.

In the process of the present invention for producing a poly(ethylenearomatic dicarboxylate ester) resin, the transesterification reaction ispreferably carried out under a pressure of 0.05 to 0.20 MPa.

In the process of the present invention for producing a poly(ethylenearomatic dicarboxylate ester) resin, the dialkylester of the aromaticdicarboxylic acid to be subjected to the transesterification reactionpreferably comprises dimethyl terephthalate in an amount of 80 molar %or more based on the total molar amount of the dialkylester of thearomatic dicarboxylic acid.

In the process of the present invention for producing a poly(ethylenearomatic dicarboxylate ester) resin, the dialkylester of the aromaticdicarboxylic acid to be subjected to the transesterification reactionpreferably contains dialkyl terephthalate recovered by depolymerizingpolyalkylene terephthalate in an amount of 70 molar % or more based onthe total molar amount of the dialkylester of the aromatic dicarboxylicacid.

In the process of the present invention for producing a poly(ethylenearomatic dicarboxylate ester) resin, the recovered dialkyl terephthalatepreferably contains 2-hydroxyterephthalic acid in a content controlledto 2 ppm or less.

In the process of the present invention for producing a poly(ethylenearomatic dicarboxylate ester) resin, preferably, the catalyst systemcomprises a non-reacted mixture of the titanium compound component (1)with the phosphorus compound component (2a) or (2b);

the whole amount of the titanium compound component (1) is added intothe reaction system before or at the start of the transesterification;and

the whole amount of the phosphorus compound component (2a) or (2b) isadded into the resultant reaction system from the transesterificationreaction before or at the start of the polycondensation reaction.

In the process of the present invention for producing a poly(ethylenearomatic dicarboxylate ester) resin, preferably, the catalyst systemcomprises a reaction product of the titanium compound component (1) withthe phosphorus compound component (2a);

the whole amount of the catalyst system is added into the reactionsystem before or at the start of the transesterification reaction; and

after the transesterification reaction is completed, the resultantreaction mixture is subjected to the polycondensation reaction.

In the process of the present invention for producing a poly(ethylenearomatic dicarboxylate ester) resin, preferably, before thetransesterification reaction, a portion of the titanium compoundcomponent (1), or a portion the reaction product of the titaniumcompound component (1) with the phosphorus compound component (2a), or aportion the phosphorus compound component (2b) is added into thereaction system, and at least one stage during and after the completionof the transesterification reaction and before and during thepolycondensation reaction, the remaining portion of the above-mentionedcatalyst component is added into the reaction system.

In the process of the present invention for producing a poly(ethylenearomatic dicarboxylate ester) resin, preferably, the whole amount of thephosphorus compound component (2a) is added into the diesterificationreaction system before the start of the diesterification reaction, or aportion of the phosphorus compound component (2a) is added into thediesterification reaction system before the start of the reaction, andthe remaining portion of the phosphorus compound component (2a) isadded, at least one stage during and after the completion of thediesterification reaction and before the start of and during thepolycondensation reaction, into the reaction system.

The poly(ethylene aromatic dicarboxylate ester) resin of the presentinvention is produced by the process for producing a poly(ethylenearomatic dicarboxylate ester) resin, as mentioned above.

The poly(ethylene aromatic dicarboxylate ester) resin of the presentinvention optionally further comprises an antioxidant hindered phenolcompound in a content of 1% by mass or less.

In the process of the present invention for producing a poly(ethylenearomatic dicarboxylate ester) resin, poly(ethylene aromaticdicarboxylate ester) resin preferably contains antimony element andgermanium element each in a content controlled to 5/1000 molar % orless.

Polyester fibers of the present invention comprises a poly(ethylenearomatic dicarboxylate ester) resin as mentioned above.

In the polyester fibers of the present invention, the poly(ethylenearomatic dicarboxylate ester) resin preferably comprises, as a principalcomponent, polyethylene terephthalate.

The polyester film of the present invention comprises a poly(ethylenearomatic dicarboxylate ester) resin as mentioned above.

In the polyester film of the present invention the poly(ethylenearomatic dicarboxylate ester) resin preferably comprises, as a principalcomponent, polyethylene terephthalate.

The bottle-formed polyester article of the present invention comprises apoly(ethylene aromatic dicarboxylate aster) resin as mentioned above.

In the bottle-formed polyester article of the present invention thepoly(ethylene aromatic dicarboxylate ester) resin preferably comprises,as a principal component, polyethylene terephthalate.

BEST MODE FOR CARRYING OUT THE INVENTION

In the process of the present invention, a poly(ethylene aromaticcarboxylate ester) resin is produced by polycondensing a diester of anaromatic dicarboxylic acid with ethylene glycol in the presence of acatalyst system.

The catalyst system used in the process of the present inventioncomprises at least one member selected from the group consisting of:

non-reacted mixtures and reaction products of (1) a titanium compoundcomponent comprising at least one member selected from the groupconsisting of titanium alkoxides and reaction products of titaniumalkoxides with aromatic polyvalent carboxylic acids or anhydridesthereof with (2a) a phosphorus compound component comprising at leastone member selected from the compounds represented by the generalformula (1):

wherein R¹, R² and R³ respectively and independently from each otherrepresent an alkyl group having 1 to 4 carbon atoms and X represents a—CH₂— group or a group represented by the formula (1a):

andnon-reacted mixtures of the above-mentioned titanium compound component(1) with (2b) a phosphorus compound component comprising at least onemember selected from the phosphorus compounds represented by the generalformulae (2) and (3):

wherein in the formula (2), R⁴ represents an alkyl group having 2 to 18carbon atoms or an aryl group having 6 to 20 carbon atoms, n representsan integer of 1 or 2 and when n represents 1, p represents an integer of0 or 1 and when n represents 2, p represents zero, and in the formula(3), m, ma and mb respectively and independently from each otherrepresents an integer of 1 or 2.

The contents of the titanium element and phosphorus element contained inthe catalyst system used in the process of the present invention arecontrolled so as to satisfy the requirements (a), (b) and (c):2≦M_(Ti)≦15  (a)1≦(M_(p)/M_(Ti))≦15  (b)10≦(M_(Ti)+M_(p))≦100  (c)in which requirements (a), (b) and (c), M_(Ti) represents a ratio of theamount in the units of milli moles of titanium element contained in thecatalyst system to the total amount in the units of moles of therepeating ethylene aromatic dicarboxylate ester units in thepoly(ethylene aromatic dicarboxylate ester), M_(p) represents a ratio ofthe amount of phosphorus element in the units of milli moles containedin the catalyst system to the total amount in the units of moles of therepeating ethylene aromatic dicarboxylate ester units in thepoly(ethylene aromatic dicarboxylate ester).

In the formula (a), M_(Ti) is a value corresponding to the total amountof the titanium compound component used in the transesterificationreaction and the polycondensation reaction of the process of the presentinvention. The value of M_(Ti) is preferably 2 or more and 15 or less,more preferably 3 or more and 10 or less, and most preferably 3 or moreand 6 or less. When the value of M_(Ti) is less than 2, the productionyield of the objective polyester resin becomes insufficient, sometimes,and a molecular weight of the resulting polyester does not reach adesired value, sometimes. On the other hand, when the value of M_(Ti)exceeds 15, the thermal stability of the resulting polyester becomesinsufficient and a molecular weight is drastically lowered, sometimes,when this polyester resin is subjected to forming at high temperature,for example, melt spinning, melt film-forming or melt bottle-forming,and thus a formed product having desired mechanical properties can notbe obtained.

In the formula (b), the value of M_(Ti) is as described above and is avalue corresponding to the total amount of the phosphorus compoundcomponent (2a) or (2b) used in the transesterification reaction and thepolycondensation reaction in the process of the present invention. Aratio M_(p)/M_(Ti) is preferably 15 or less, more preferably 2 or moreand 15 or less, and most preferably 4 or more and 10 or less. When theratio M_(p)/M_(Ti) is less than 1, the resulting polyester resin has anyellowish color tone. On the other hand, when it exceeds 15, thepolycondensation activity of the catalyst system is not enough to obtaina polyester of the catalyst system, and thus making it difficult toobtain a polyester having a desired molecular weight. When M_(p)/M_(Ti)is within a range from 1 to 15, the polymerization activity of thecatalyst system to a diester of an aromatic dicarboxylic acid andethylene glycol of the catalyst system becomes sufficiently high and apolyester resin having a desired molecular weight and a good color tonecan be obtained.

Furthermore, in the formula (c), the sum of M_(Ti) and M_(p),(M_(Ti)+M_(p)), is preferably 10 or more and 100 or less, and morepreferably 2 or more and 70 or less. When the value of (M_(Ti)+M_(p)) isless than 10, the uniformity of the quality and the formability of theresulting polyester resin become insufficient and the production yieldbecomes insufficient when the resulting polyester resin is subjected tofilm-forming using an electrostatic impression process. Also theresulting film has not a uniform thickness and, therefore, the resultingfilm has insufficient film-formability and insufficient impactresistance. On the other hand, when the value of (M_(Ti)+M_(p)) exceeds100, the resulting polyester resin contains foreign matters, whichoriginates from the polymerization catalyst, resulting in insufficienttransparency.

The aromatic dicarboxylic acid used in the process of the presentinvention is preferably selected from terephthalic acid, isophthalicacid, naphthalene dicarboxylic acid, 5-sulphoisophthalate metal salt and5-sulphoisophthalate onium salt.

The process of the present invention may further comprise the step ofproducing the diester of the aromatic dicarboxylic acid with ethyleneglycol by a diesterification reaction of the aromatic dicarboxylic acidwith ethylene glycol.

This diesterification reaction of the aromatic dicarboxylic acid withethylene glycol may be carried out in the absence of a catalyst or thepresence of a catalyst (for example, alkali metal salt or alkali earthmetal salt) under the reaction conditions of a pressure of 0.05 to 0.20MPa and a temperature of 230 to 280° C.

In another embodiment, the process of the present invention may furthercomprises the step of producing the diester of an aromatic dicarboxylicacid with ethylene glycol by a transesterification reaction of adialkylester of an aromatic dicarboxylic acid with ethylene glycol.

In this transesterification reaction, transesterification of adialkylester of an aromatic dicarboxylic acid with ethylene glycol iscarried out at a temperature of 160 to 260° C. under a pressure of 0.05to 0.20 MPa in the presence of a catalyst.

When the pressure during the transesterification reaction is less than0.05 MPa, the reaction may not be sufficiently promoted by a catalyticaction of the titanium compound component (1), sometimes. On the otherhand, when the pressure exceeds 0.20 MPa, a large amount of diethyleneglycol as by-product may be produced, and thus the resulting polymer mayhave unsatisfactory properties, for example, an unsatisfactory thermalstability.

In the process of the present invention, when using a dialkylester of anaromatic dicarboxylic acid, an alkyl group preferably has 1 to 5 carbonatoms and, more preferably, methyl group, ethyl group or isopropyl groupis used. Preferred dialkylester of the aromatic dicarboxylic acid usedin the process of the present invention is preferably selected fromdimethyl terephthalate, dimethyl isophthalate dimethyl naphthalate,diethyl terephthalate, diethyl isophthalate and diethyl naphthalate.

In the process of the present invention, the dialkylester of thearomatic dicarboxylic acid to be subjected to the transesterificationreaction may comprise dimethyl terephthalate in an amount of 80 molar %or more based on the total molar amount of the dialkylester of thearomatic dicarboxylic acid.

The dialkylester of the aromatic dicarboxylic acid to be subjected tothe transesterification reaction may contain dialkyl terephthalaterecovered by depolymerizing polyalkylene terephthalate in an amount of70 molar % or more based on the total molar amount of the dialkylesterof the aromatic dicarboxylic acid.

The recovered dialkyl terephthalate preferably contains2-hydroxyterephthalic acid in a content controlled to 2 ppm or less.

In the process of the present invention, when the diester of thearomatic dicarboxylic acid with ethylene glycol is produced by thetransesterification reaction of the aromatic dialkylester with ethyleneglycol, this transesterification reaction is usually carried out in thepresence of a catalyst. As the catalyst for the transesterificationreaction, all or a portion of the catalyst system for polycondensationused in the process of the present invention can be employed.

In the process of the present invention, namely, the transesterificationreaction of the dialkylester of the aromatic dicarboxylic acid withethylene glycol is preferably carried out in the presence of thetitanium compound component (1), which is not reacted with at least thephosphorus compound component (2a) or (2b) in the catalyst system orreacted with the phosphorus compound component (2a); and

the resultant reaction mixture from the transesterification reaction andcontaining the diester of the aromatic dicarboxylic acid with ethyleneglycol is subjected to a polycondensation reaction in the presence of acatalyst system comprising, together with at least the non-reacted orreacted titanium compound component (1) contained in the reactionmixture, the non-reacted or reacted phosphorus compound component (2a)or the non-reacted phosphorus compound component (2b) to produce apoly(ethylene aromatic dicarboxylate ester) resin.

In the process of the present invention, the titanium compound component(1), which constitutes the catalyst system, comprises at least onemember selected from the group consisting-of titanium alkoxides andreaction products of titanium alkoxides with aromatic polyvalentcarboxylic acids or anhydrides thereof.

In the present invention, the titanium alkoxides used in the titaniumcompound component (1), which constitutes the catalyst system, arepreferably selected from the titanium compounds represented by thegeneral formula (4):

in which formula (4), R⁵, R⁶, R⁷ and R⁸ respectively and independentlyfrom each other represent an alkyl group having 2 to 10 carbon atoms ora phenyl group, and mc represents an integer of 1 to 4. As the titaniumalkoxides, for example, tetraisopropoxytitanium, tetrapropoxytitanium,tetra-n-butoxytitanium, tetraethoxytitanium, tetraphenoxytitanium,octaalkyl trititanate and hexaalkyl dititanate are preferably used.

In the process of the present invention, the aromatic polyvalentcarboxylic acids used in the titanium compound component (1), whichconstitutes the catalyst system, are selected from the compoundsrepresented by the general formula (5):

in which formula (5), na represents an integer of 2 to 4.

The aromatic polyvalent carboxylic acids or anhydrides thereof arepreferably selected from phthalic acid, trimellitic acid, hemimelliticacid, pyromellitic acid and anhydrides thereof.

The reaction of the titanium alkoxide with the aromatic polyvalentcarboxylic acid (or anhydride thereof) is carried out by mixing thearomatic polyvalent carboxylic acid or anhydride thereof with a solvent,thereby to dissolve all or a portion of the aromatic polyvalentcarboxylic acid in the solvent, adding dropwise the titanium alkoxide tothe mixed solution and maintaining at a temperature of 0 to 200° C. for30 or more minutes, and preferably at 30 to 150° C. for 40 to 90minutes. The reaction pressure is not specifically limited and may benormal pressure. The solvent is selected from those capable ofdissolving a portion or all of the aromatic polyvalent carboxylic acidor anhydride thereof, and is preferably selected ethanol, ethyleneglycol, trimethylene glycol, tetramethylene glycol, benzene and xylene.

A reaction molar ratio of the titanium alkoxide to the aromaticpolyvalent carboxylic acid or anhydride thereof is not specificallylimited. However, when the proportion of the titanium alkoxide is toohigh, the resulting polyester may have poor color tone and a lowsoftening point. On the other hand, when the proportion of the titaniumalkoxide is too low, the polycondensation reaction sometimes hardlyproceeds. Therefore, the reaction molar ratio of the titanium alkoxideto the aromatic polyvalent carboxylic acid or anhydride thereof ispreferably controlled within a range from 2/1 to 2/5. The reactionproduct obtained by the reaction may be subjected as it is to thereaction with the above-mentioned phosphorus compound component (2a), orthe reaction product may be reacted with the phosphorus compoundcomponent (2a) after purifying by recrystallization with a solventcomprising acetone, methyl alcohol and/or ethyl acetate.

In an embodiment of the catalyst system used in the process of thepresent invention, a non-reacted mixture or a reaction product of thetitanium compound component (1) with the phosphorus compound component(2a) is used. The phosphorus compound component (2a) contains at leastone member selected from the phosphorus compound represented by thegeneral formula (1).

The phosphorus compound (phosphonate compound) represented by thegeneral formula (1) is preferably selected from dimethylesters,diethylesters, dipropylesters and dibutylesters ofcarbomethoxymethanephosphonic acid, carboethoxymethanephosphonic acid,carbopropoxymethanephosphonic acid, carbobutoxymethanephosphonic acid,carbomethoxy-phosphono-phenylacetic acid,carboethoxy-phosphono-phenylacetic acid,carbopropotoxy-phosphono-phenylacetic acid andcarbobutoxy-phosphono-phenylacetic acid.

The phosphorus compound (phosphonate compound) represented by thegeneral formula (1) reacts with the titanium compound component (1),relatively mildly, and thus making it possible to extend the duration ofthe catalytic activity of the titanium compound during thepolycondensation reaction and to reduce the amount of the catalystsystem to be added during the polyester polymerization reaction. Even ifa large amount of stabilizers is added to the catalyst system containingthe phosphorus compound of the formula (1), the thermal stability of theresulting polyester is not lowered and the color tone is not madeinsufficient.

The reaction product of the titanium compound component (1) with thephosphorus compound component (2a) is produced, for example, by mixingthe phosphorus compound component (2a) comprising at least one memberselected from the phosphorus compound of the formula (1) with a solvent,thereby to dissolve all or a portion of the phosphorus compoundcomponent (2a) in the solvent, adding dropwise the titanium compoundcomponent (1) to the mixed solution and maintaining the reaction systemat a temperature of 50 to 200° C., preferably at 70 to 150° C., for oneminute to 4 hours, preferably 30 minutes to 2 hours. In the reaction,although the reaction pressure is not specifically limited and may beany of pressure (0.1 to 0.5 MPa), the ambient atmospheric pressure andreduced pressure (0.001 to 0.1 MPa), the reaction is usually carried outunder the ambient atmospheric pressure.

The solvent for the phosphorus compound component (2a) of the formula(1) used in the reaction for production of the catalyst is notspecifically limited as far as it can dissolve at least a portion of thephosphorus compound component (2a). For example, a solvent comprising atleast one member selected from ethanol, ethylene glycol, trimethyleneglycol, tetramethylene glycol, benzene and xylene is preferably used.Particularly, the same compound as a glycol component, which constitutesthe polyester to be finally obtained, is preferably used as the solvent.

In the reaction for production of the catalyst, preferably the ratio ofthe titanium compound component (1) to the phosphorus compound component(2a) in the reaction system is controlled so that a reaction molar ratioof a molar amount calculated in terms of titanium atom (m_(Ti)) of thetitanium compound component (1) to a molar amount calculated in terms ofphosphorus atom (m_(p)) of the phosphorus compound component (2a),m_(Ti)/m_(p), is within a range from 1:1 to 1:3, and preferably from 1:1to 1:2 in the reaction product of the titanium compound component (1)with the phosphorus compound component (2a) contained in the resultingcatalyst.

The reaction product of the titanium compound component (1) with thephosphorus compound component (2a) may be used as the catalyst forproduction of the polyester without purifying after being separatingfrom the reaction system using a means such as centrifugal sedimentationor filtration. Alternatively, the separated reaction product may be usedas the catalyst after purifying by recrystallization with arecrystallizing agent, for example, acetone, methyl alcohol and/orwater. Also the reaction product-containing reaction mixture may be usedas it is as a catalyst-containing mixture without separating thereaction product from the reaction system.

In the catalyst system used in the process of the present invention, thetitanium compound component (1) and the phosphorus compound component(2a) may be used as the non-reacted mixture. In this case, a ratio ofthe titanium compound component (1) to the phosphorus compound component(2a) is controlled so that a ratio of a molar amount calculated in termsof titanium atom (m_(Ti)) of the titanium compound component (1) to amolar amount calculated in terms of phosphorus atom (m_(p)) of thephosphorus compound component (2a), m_(Ti)/m_(p), is within a range from1:1 to 1:15, and more preferably from 1:2 to 1:10.

In another aspect of the catalyst used in the process of the presentinvention, the titanium compound component (1) is used after mixing withthe phosphorus compound component (2b) comprising at least one memberselected from the phosphorus compounds represented by the generalformula (2) or (3).

Specific examples of the phosphorus compounds represented by the generalformula (2) include phenylphosphonic acid, methylphosphonic acid,ethylphosphonic acid, propylphosphonic acid, isopropylphosphonic acid,butylphosphonic acid, tolylphosphonic acid, xylylphosphonic acid,biphenylphosphonic acid, naphthylphosphonic acid, anthrylphosphonicacid, 2-carboxyphenylphosphonic acid, 3-carboxyphenylphosphonic acid,4-carboxyphenylphosphonic acid, 2,3-dicarboxyphenylphosphonic acid,2,4-dicarboxyphenyl phosphonic acid, 2,5-dicarboxyphenyl phosphonicacid, 2,6-dicarboxyphenyl phosphonic acid, 3,4-dicarboxyphenylphosphonic acid, 3,5-dicarboxyphenyl phosphonic acid,2,3,4-tricarboxyphenyl phosphonic acid, 2,3,5-tricarboxyphenylphosphonic acid, 2,3,6-tricarboxyphenyl phosphonic acid,2,4,5-tricarboxyphenyl phosphonic acid and 2,4,6-tricarboxyphenylphosphonic acid in case p represents 0. Among these compounds,monoarylphosphonic acid is preferred.

Specific examples of the other phosphorus compounds represented by thegeneral formula (2) include monomethyl phosphate, monoethyl phosphate,monotrimethyl phosphate, mono-n-butyl phosphate, monohexyl phosphate,monoheptyl phosphate, monononyl phosphate, monodecyl phosphate,monodoedcyl phosphate, monophenyl phosphate, monobenzyl phosphate,mono(4-dodecyl)phenyl phosphate, mono(4-methyl)phenyl phosphate,mono(4-ethyl)phenyl phosphate, mono(4-propyl)phenyl phosphate,mono(4-dodecylphenyl) phosphate, monotolyl phosphate, monoxylylphosphate, monobiphenyl phosphate, mononaphthyl phosphate andmonoanthryl phosphate in case p represents 1.

Specific examples of the phosphorus compound of the geenral formula (3)include tri(hydroxyethoxy) phosphate and tri(hydroxyethoxyethoxy)phosphate.

In the catalyst system used in the process of the present invention, thetitanium compound component (1) and the phosphorus compound component(2b) may be used in a non-reacted mixture thereof. In this case, themixing of the titanium compound component (1) to the phosphorus compoundcomponent (2b) is preferably controlled so that the ratio of a molaramount calculated in terms of titanium atom (m_(Ti)) of the titaniumcompound component to a molar amount calculated in terms of phosphorusatom (m_(p)) of the phosphorus compound component, m_(Ti)/m_(p), iswithin a range from 1:1 to 1:15, and more preferably from 1:2 to 1:10.

Even if the phosphorus compound components (2a) and (2b) containing thephosphorus compounds of the general formulae (1), (2) and (3) coexist asa reaction product or non-reacted mixture with the titanium compoundcomponent (1) in the transesterification reaction of the dialkylester ofthe aromatic dicarboxylic acid with ethylene glycol, they do not exertan adverse influence on the transesterification reaction and alsoexhibit a strong catalytic activity, together with the titanium compoundcomponent (1), in the polycondensation reaction of the diester of thearomatic dicarboxylic acid with ethylene glycol.

In the process for producing the polyester of the present invention, apolymerization starting material comprising the diester of the aromaticdicarboxylic acid with ethylene glycol (or may be a low polymer(oligomer) thereof) is polycondensed in the presence of the catalyst.

The polycondensation reaction is preferably carried out at a temperatureof 230 to 320° C. under normal pressure or reduced pressure, preferably0.05 Pa to 0.2 MPa, or under the combined conditions for 15 to 300minutes.

In the process of the present invention, in case the catalyst systemcomprises a non-reacted mixture of the titanium compound component (1)with the phosphorus compound component (2a) or (2b), optionally, thewhole amount of the titanium compound component (1) is added into thereaction system before or at the start of the transesterification, andthe whole amount of the phosphorus compound component (2a) or (2b) isadded into the resultant reaction system from the transesterificationreaction before or at the start of the polycondensation reaction.

In case the catalyst system comprises a reaction product of the titaniumcompound component (1) with the phosphorus compound component (2a),optionally, the whole amount of the catalyst system is added into thereaction system before or at the start of the transesterificationreaction and

after the transesterification reaction is completed, the resultantreaction mixture is subjected to the polycondensation reaction.

In the process of the present invention, in case the diester of thearomatic dicarboxylic acid with ethylene glycol is produced by thetransesterification reaction, optionally, before the transesterificationreaction, a portion of the titanium compound component (1), or a portionthe reaction product of the titanium compound component (1) with thephosphorus compound component (2a), or a portion the phosphorus compoundcomponent (2a) is added into the reaction system, and at least one stageduring and after the completion of the transesterification reaction andbefore and during the polycondensation reaction, the remaining portionof the above-mentioned catalyst component is added into the reactionsystem.

In the process of the present invention, in case the diester of thearomatic dicarboxylic acid with ethylene glycol is produced by thediesterification reaction, optionally, the whole amount of thephosphorus compound component (2a) is added into the diesterificationreaction system before the start of the diesterification reaction, or aportion of the phosphorus compound component (2a) is added into thediesterification reaction system before the start of the reaction, andthe remaining portion of the phosphorus compound component (2a) isadded, at least one stage during and after the completion of thediesterification reaction and before the start of and during thepolycondensation reaction, into the reaction system.

According to the process of the present invention as mentioned above, apoly(ethylene aromatic carboxylate ester) resin having a good color toneis obtained without forming foreign matters (or with forming lessforeign matters) which originate from the catalyst system used.

If necessary, reaction stabilizers such as trimethyl phosphate may beadded into the polyester resin of the present invention in any stageduring the production of the polyester resin and, if necessary, one ormore members selected from additives such as antioxidants, ultravioletabsorbers, flame retardants, fluorescent whitening agents, mattingagents, color-regulating agents, defoaming agents and the like. It isparticularly preferred that the polyester contains an antioxidantcontaining at least one member selected from hindered phenol compounds,and the content is preferably 1% by mass or less based on the mass ofthe polyester. When the content exceeds 1% by mass, there sometimesarises a problem in that thermal deterioration of the antioxidant itselfcauses the quality of the resulting product to be degraded. The hinderedphenol compound for antioxidant used in the present invention can beselected frompentaerythritol-tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate,3,9-bis{2-[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy]-1,1-dimethylethyl}-2,4,8,10-tetraoxaspiro[5,5]undecane,1,1,3-tris(2-methyl-4-hdyroxy-5-tert-butylphenyl)butane,1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene,1,3,5-tris-(4-tert-butyl-3-hydroxy-2,6-dimethylbenzene)isophthalic acid,triethyl glycol-bis[3-(3-tert-butyl-5-methyl-4-hydroxyphenyl)propionate,1,6-hexanediol-bis[3-(3,5-di-tert-butyl-4-hdyroxyphenyl)propionate],2,2-thio-diethylene-bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]and octadecyl[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]. Thesehindered phenol antioxidants are preferably used in combination withthioether secondary antioxidants.

Although the method of adding the hindered phenol antioxidant into thepolyester is not specifically limited, the hindered phenol antioxidantis preferably added in any stage during or after the completion of thetransesterification reaction and before the completion of thepolycondensation reaction.

To finely control the color tone of the resulting polyester,color-regulating agents comprising one or more members selected fromorganic and inorganic blue pigments such as azo, triphenylmethane,quinoline, anthraquinone and phthalocyanine pigments can be added intothe reaction system in the stage of producing the polyester. In theprocess of the present invention, as a matter of course, it is notnecessary to use an inorganic blue pigment containing Co, which lowersthe melt thermal stability of the polyester, as the color-regulatingagent. Therefore, the polyester obtained by the process of the presentinvention is substantially free from cobalt.

In the polyester obtained by the process of the present invention, thevalue L obtained by a Hunter type calorimeter is usually 80.0 or moreand the value b is usually within a range from −2.0 to 5.0. When thevalue L of the polyester is less than 80.0, a high whiteness formedarticle, which can be put into practice, can not be obtained sometimesbecause the resulting polyester has poor whiteness. When the value b isless than −2.0, the resulting polyester has less yellowish tint, but abluish tint increases. On the other hand, when the value b exceeds 5.0,the resulting polyester can not be used in the production of apractically useful formed article, sometimes, because of strongyellowish tint. The value L of the polyester obtained by the process ofthe present invention is preferably 82 or more, and particularlypreferably 83 or more, while the value b is preferably within a rangefrom −1.0 to 4.5, and particularly preferably from 0.0 to 0.4.

The value L and the value b of the polyester obtained by the process ofthe present invention are measured by the following procedure. That is,a polyester sample is melted at 290° C. under vacuum for 10 minutes andformed into a plate having a thickness of 3.0±1.0 mm on an aluminumplate. The polyester specimen is immediately quenched in ice water,dried at 160° C. for one hour, subjected to a crystallization treatmentand then placed on a white standard plate for adjusting a colorimeter.The color tone of the surface of the plate-like specimen on the standardplate is measured by using a calorimeter, for example, Hunter type colordifference meter, CR-200 manufactured by Minolta Co., Ltd.

The intrinsic viscosity of the polyester in the present invention is notspecifically limited, but is preferably within a range from 0.50 to 1.0.When the intrinsic viscosity is within the above range, melt forming canbe easily carried out and the resulting formed article has a highstrength. The intrinsic viscosity is more preferably within a range from0.52 to 0.9, and particularly preferably from 0.05 to 0.8.

The intrinsic viscosity of the polyester is measured at a temperature of35° C. after dissolving the polyester to be tested inortho-chlorophenol.

The polyester produced by solid phase polycondensation is generally usedin the production of bottles, and therefore, it is preferred that thecontent of cyclic trimer of an ester of the aromatic dicarboxylic acidwith ethylene glycol contained in the polyester and having an intrinsicviscosity of 0.70 to 0.90 is 0.5% by weight or less, and the content ofacetaldehyde in the polyester is 5 ppm or less.

The poly(ethylene aromatic dicarboxylate ester) resin produced by theprocess of the present invention preferably contains antimony elementand germanium element, as impurities, each in a content controlled to5/1000 molar % or less, and more preferably 2/1000 molar % or less.

When the content of antimony element and germanium element in thepolyester exceeds 5/1000 molar %, the resulting polyester may have adark blackish color peculiar to antimony element and incorporation ofgermanium element causes a problem such as increase in manufacturingcost of the resulting polyester.

As described above, the content of antimony element and germaniumelement in the poly(ethylene aromatic dicarboxylate ester) resin iscontrolled to 5/1000 molar % or less by controlling the content ofantimony element and germanium element in the diester of the aromaticdicarboxylic acid with ethylene glycol to be subjected to thepolycondensation reaction.

Polyester fibers can be produced from the poly(ethylene aromaticdicarboxylate ester) resin of the present invention.

In this case, the poly(ethylene aromatic dicarboxylate ester) resinpreferably comprises, as a principal component, polyethyleneterephthalate.

A polyester film can be produced from the poly(ethylene aromaticdicarboxylate ester) resin of the present invention.

In this case, the poly(ethylene aromatic dicarboxylate ester) resinpreferably comprises, as a principal component, polyethyleneterephthalate.

A bottle-formed polyester article can be produced from the poly(ethylenearomatic dicarboxylate ester) resin of the present invention.

In this case, the poly(ethylene aromatic dicarboxylate ester) resinpreferably comprises, as a principal component, polyethyleneterephthalate.

In an embodiment (1) of the process of the present invention, apolyethylene terephthalate resin is produced by using an ester of anaromatic dicarboxylic acid with ethylene glycol, which preferablycontains, as a polycondensation material, ethylene terephthalate in anamount of 80 molar % or more, more preferably 85 molar % or more, andlimiting each content of the antimony element and germanium element to5/1000 molar % or less, while using the catalyst system and controllingthe catalyst system so as to meet the above requirements (a), (b) and(c). In this embodiment (1), when the ester of the aromatic dicarboxylicacid with ethylene glycol is produced by the transesterificationreaction, it is controlled that dimethyl terephthalate accounts for 80molar % or more of the alkylester of the aromatic dicarboxylic acid. Inthis transesterification reaction, a portion or all of the titaniumcompound component (1) of the catalyst system used in the process of thepresent invention is added to the transesterification reaction systemand the transesterification reaction is carried out under a pressure of0.05 to 0.20 MPa and the resulting ester of the aromatic dicarboxylicacid with ethylene glycol is subjected to the polycondensation reaction.

The polyethylene terephthalate resin obtained in the embodiment (1)preferably contains an ethylene terephthalate resin in an amount of 80molar % or more, more preferably 85 molar % or more, and may be mixedwith other resins other than the ethylene terephthalate resin. Thepolyethylene terephthalate resin means a polyester having an ethyleneterephthalate structure as a principal repeating unit. As used herein,the principal repeating units contain ethylene terephthalate units in anamount of 80 molar % or more, more preferably 85 molar % or more, of thewhole repeating units. In case where the polyethylene terephthalateresin is obtained by copolymerizing a third component other than theethylene terephthalate component, there can be used, the third component(copolymerization component) may be selected from aromatic dicarboxylicacid other than terephthalic acid, such as 2,6-naphthalenedicarboxylicacid, isophthalic acid or phthalic acid; aliphatic dicarboxylic acidsuch as adipic acid, azelaic acid, sebacic acid or decanedicarboxylicacid; and alicyclic dicarboxylic acid such as cyclohexanedicarboxylicacid.

The polyester resin of the embodiment (1) preferably has an intrinsicviscosity (o-chlorophenol, 35° C.) within a range from 0.50 to 0.80,more preferably from 0.55 to 0.75, and particularly preferably from 0.60to 0.70.

In case the polyethylene terephthalate resin of the embodiment (1) isused to form a film, it may contain, as a lubricant, inert particleshaving an average particle diameter of 0.05 to 5.0 μm in an amount ofabout 0.05 to 5.0% by weight, for the purpose of improving the handlingproperty. For the purpose of maintaining high transparency as a featureof the polyethylene terephthalate resin of the present invention, theparticle size of the inert particle is prefarably as small as possibleand the amount of the inert particles is preferably as small aspossible. The examples of the inert particles used as the lubricantinclude colloidal silica, porous silica, titanium oxide, calciumcarbonate, calcium phosphate, barium sulfate, alumina, zirconia, kaolin,complex oxide particles, crosslinked polystyrene, crosslinked acrylicresin particles, crosslinked methacrylic resin particles and siliconeparticles. In case where the polyethylene terephthalate resin is used invarious formed articles, for example, films, fibers and bottles, ifnecessary, it may contain various functional agents, for example,antioxidants, thermal stabilizers, viscosity modifiers, plasticizers,color hue modifiers, nucleating agents and ultraviolet absorbers.

In an embodiment (2) of the present invention, a diester of terephthalicacid with ethylene glycol is produced by the transesterificationreaction (pressure: 0.05 to 0.20 MPa) of an dialkylester of terephthalicacid, preferably dimethyl terephthalate, with ethylene glycol using acatalyst system comprising non-reacted mixtures or reaction products ofthe titanium compound component (1) with the phosphorus compoundcomponent (2a) and, furthermore, the diester is polycondensed to producea polyethylene terephthalate resin. At this time, the composition of thecatalyst system is controlled so as to meet the constituent elements(a), (b) and (c). Polyester fibers are produced from the polyethyleneterephthalate resin.

The polyester resin preferably has an intrinsic viscosity within a rangefrom 0.40 to 0.80, more preferably from 0.45 to 0.75, and particularlypreferably from 0.50 to 0.70. The intrinsic viscosity of less than 0.40is not preferred because the resulting fibers may have an insufficientstrength. On the other hand, when the intrinsic viscosity exceeds 0.80,the intrinsic viscosity of a raw polymer may be excessively high and itmay be uneconomical.

In the embodiment (2) of the process of the present invention, theprocess for producing polyester fibers is not specifically limited and aconventionally known process for melt-spinning a polyester can be used.For example, it is preferred that a polyester is melted at a temperaturewithin a range from 270 to 300° C. and the molten polyester is spunwhile controlling a melt spinning rate within a range from 400 to 5000m/min. When the spinning rate is within the above range, the resultingfibers have sufficient strength and can be wound up under stableconditions. The stretched yarn can be produced or by continuouslystretching the polyester fibers after winding up the fibers or withoutwinding up the fiber. Furthermore, the polyester fibers of the presentinvention may be subjected to a weight reduction treatment with alkalito cause the softness of the fibers to increase.

In the production of the polyester fibers, the shape of spinningorifices of the spinneret is not specifically limited and may be acircular or non-circular, or a spinning orifice for hollow fibers may beused.

In an embodiment (3) of the present invention, a diester of an aromaticdicarboxylic acid such as terephthalic acid with ethylene glycol, or anoligomer of the diester is produced, for example, by the esterificationreaction of high purity terephthalic acid with ethylene glycol, and thenthe diester or an oligomer thereof is subjected to the polycondensationreaction. In this polycondensation, the diester or oligomer ispolycondensed in the presence of a polycondensation catalyst systemcomprising a reaction product of a titanium compound componentcomprising a titanium alkoxide represented by the general formula (4)with a phosphorus compound component comprising a phosphorus compoundrepresented by the general formula (1) in a glycol solvent, to produce apoly(ethylene aromatic dicarboxylate ester) resin. The resulting apoly(ethylene aromatic dicarboxylate ester) resin is subjected to afilm-forming step to produce a polyester film.

In the embodiment (3), a molar ratio of phosphorus atoms to titaniumatoms, which are contained in the catalyst system, is preferably 1.0 ormore and less than 8.0, and more preferably 2.0 or more and less than7.0.

When the reaction product is contaminated with the non-reacted titaniumcompound component (1), the resulting polyester resin may haveunsatisfactory color tone. When the reaction product is contaminatedwith the non-reacted phosphorus compound component (2a), thepolycondensation reaction of the ester of terephthalic acid withethylene glycol may be inhibited.

The reaction of the titanium compound component (1) with the phosphoruscompound component (2a) proceeds by mixing the titanium compoundcomponent (1) with the phosphorus compound component (2a) and heatingthe mixture. The reaction product usually exists in a solution state. Toallow the reaction to proceed uniformly, it is preferred to use aprocess in which a glycol solvent solution of the titanium compoundcomponent (1) and a glycol solvent solution of the phosphorus compoundcomponent (2a) are prepared respectively and the mixture is heated. Whenthe reaction temperature is room temperature, there arises a problemthat the reaction proceeds insufficiently and the reaction requiresexcessive long time. Therefore, in order to uniformly and efficientlyobtain a reaction product, the reaction is preferably carried out at atemperature within a range from 50 to 200° C. and the reaction time ispreferably within a range from 1 minute to 4 hours. When using ethyleneglycol as a glycol, the reaction temperature is preferably within arange from 50 to 150° C. and, when using hexamethylene glycol as aglycol, the reaction temperature is preferably within a range from 100to 200° C. The reaction time is preferably within a range from 30minutes to 2 hours in these cases.

The catalyst system used in the embodiment (3) preferably meet theabove-mentioned requirements (a), (b) and (c).

In the embodiment (3), a polyester film can be produced bymelt-extruding a poly(ethylene aromatic dicarboxylate ester) resin andquenching the extruded resin melt stream to form an undrawn film, andbiaxially drawing the undrawn film. After drawing, the resultingpolyester film may be subjected to a heat set treatment or a relaxingheat treatment, if necessary.

As the aromatic dicarboxylic acid, for example, there can be usedterephthalic acid, phthalic acid, isophthalic acid,naphthalenedicarboxylic acid, diphenyldicarboxylic acid,diphenoxyethanedicarboxylic acid, or ester-forming derivatives thereof.

Also it is possible to use a small amount of an aliphatic dicarboxylicacid such as adipic acid, sebacic acid, azelaic acid ordecanedicarboxylic acid, and an alicyclic dicarboxylic acid such ascyclohexanedicarboxylic acid may be used in combination with thearomatic dicarboxylic acid. Also, ester-forming derivatives of theabove-mentioned compounds may be used. Further, it is possible to use asmall amount (10 molar % or less) of an alicyclic glycol such astrimethylene glycol, propylene glycol, tetramethylene glycol, neopentylglycol, hexamethylene glycol, dodecamethylene glycol or cyclohexanedimethanol, and an aromatic diol such as bisphenol, hydroquinone or2,2-bis(4-β-hydroxyethoxyphenyl)propanes in combination with ethyleneglycol.

Furthermore, a small amount (1 molar % or less) of a polyfunctionalcompound such as trimesic acid, trimethylolethane, trimethylolpropane,trimethylolmethane or pentaerythritol may be used in combination withthe aromatic dicarboxylic acid.

In the embodiment (3), the polyester constituting the polyester film ispreferably polyethylene terephthalate wherein terephthalic acid or anester-forming derivative thereof is used in an amount of 80 molar % ormore, preferably 90 molar % or more, based on 100 molar % of thearomatic dicarboxylic acid, while ethylene glycol or an ester-formingderivative thereof is used in an amount of 80 molar % or more,preferably 90 molar % or more, based on 100 molar % of the aliphaticglycol. Particularly preferred is polyethylene terephthalate producedthrough the esterification reaction so that terephthalic acid accountsfor 80 molar % of entire dicarboxylic acid component used as a rawmaterial. In comparison with polyethylene terephthalate produced byusing dimethyl terephthalate as a starting compound polyethyleneterephthalate produced by using terephthalic acid as a starting compounddoes not need a transesterification reaction catalyst and a stabilizerto be added to deactivate the transesterification reaction catalyst. Asa result, there is the advantage that an interaction between thephosphorus compound added as the stabilizer and the titanium compound issuppressed and the amount of the titanium compound can be reduced.

The process for producing a polyester through the esterificationreaction will now be described in detail.

(Esterification Procedure)

First, upon production of the polyester, an aromatic dicarboxylic acidis esterified with an aliphatic glycol. For example, a slurry containingthe aromatic dicarboxylic acid and the aliphatic glycol is prepared. Theslurry usually contains 1.1 to 1.6 moles, preferably 1.2 to 1.4 moles,of the aliphatic glycol per mole of the aromatic dicarboxylic acid. Theslurry is continuously fed to an esterification reaction procedure.

The esterification reaction is preferably carried out by a procedurewhich is carried out in a single stage while self-circulating a reactionmixture, or a procedure which is carried out by combining two or moreestertification reactors with each other in series. In both cases, thereaction is carried out while removing water produced during thereaction out of the system using a rectifying column under theconditions where an aliphatic glycol is refluxed.

In case the esterification is continuously carried out in a single stagewhile self-circulating the reaction mixture the reaction is usuallycarried out at the reaction temperature within a range from 240 to 280°C., preferably from 250 to 270° C., under the reaction pressure within arange from the ambient atmospheric pressure to 0.3 MPa. The reaction ispreferably carried out until the esterification degree reaches 90% ormore, and preferably 95% or more.

By this esterification procedure, an esterification reaction product(oligomer) of the aromatic dicarboxylic acid with the aliphatic glycolis obtained and the polymerization degree of this oligomer is preferablywithin a range from 4 to 10. The oligomer thus obtained is fed to thefollowing polycondensation step.

(Polycondensation Procedure)

In the polycondensation procedure, the oligomer obtained in theesterification procedure is polycondensed by heating to a temperaturehigher than a melting point of the polyester (usually from 240 to 280°C.) in the presence of the above-mentioned polycondensation catalyst.The polycondensation reaction is preferably carried out while distillingoff the non-reacted aliphatic glycol and the aliphatic glycol producedduring the polycondensation reaction out of the reaction system.

The polycondensation reaction may be carried out in a single reactionvessel, or may be separately carried out in plural reaction vessels. Incase the polycondensation reaction is carried out in two stages, thepolycondensation reaction in the first vessel is carried out under theconditions of the reaction temperature within a range from 245 to 290°C., preferably from 260 to 280° C., and the reaction pressure within arange from 100 to 1 kPa, preferably from 50 to 2 kPa. The finalpolycondensation reaction in the second vessel is carried out under theconditions of the reaction temperature within a range from 265 to 300°C., preferably 270 to 290° C., and the reaction pressure within a rangefrom 1000 to 10 Pa, preferably from 500 to 30 Pa.

In the manner described above, the polyester for constituting thepolyester film can be produced and the resulting polyester is formedinto granules (chips) by extruding in a molten state and then cooling.The resulting polyester preferably has an intrinsic viscosity(hereinafter referred to as IV) within a range from 0.40 to 0.80 dl/g,and more preferably from 0.50 to 0.70 dl/g.

The polyester film of the present invention may be a single-layer film,or a laminate film comprising two or more layers. In case of thelaminated film, one or more layers may comprise the polyester film ofthe present invention, and preferably all layers comprise the polyesterfilm of the present invention.

Manufacturing conditions such as drawing conditions upon forming into afilm may be appropriately established in response to physical propertiessuch as surface properties, density and thermal shrinkage, of the targetfilm. For example, the above-mentioned undrawn film is monoaxially drawn(in a longitudinal or lateral direction) at a draw ratio of 2.5 times ormore, preferably 3 times or more, at a temperature within a range from[Tg−10] to [Tg+60]° C., and then drawn in a direction perpendicular tothe above drawing direction at a draw ratio of 2.5 times or more,preferably 3 times or more, at a temperature within a range from Tg to[Tg+70]° C. If necessary, the resulting drawn film may be further drawnin a longitudinal or transverse direction. An area draw ratio which isthe product of the longitudinal draw ratio and the transverse draw ratiois preferably 9 or more, more preferably 12 to 35, and particularlypreferably 15 to 30. After drawing, the drawn film may be subjected to aheat set treatment and, if necessary, the drawn film may be subjected toa relaxing heat treatment before or after the heat set treatment. Theheat set treatment is preferably carried out at a temperature within arange from [Tg+70] to [Tm−10]° C. (Tm: melting point of polyester), forexample, 180 to 250° C. and the heat set time is preferably within arange from 1 to 60 seconds.

In the polyester film of the present invention, inert particles havingan average particle size of 0.05 to 5.0 μm may be added as a lubricantin an amount of about 0.05 to 50% by weight for the purpose of improvingthe handling property. Examples of the inert particles to be addedinclude colloidal silica, porous silica, titanium oxide, calciumcarbonate, calcium phosphate, barium sulfate, alumina, zirconia, kaolin,and complex oxide particles, crosslinked polystyrene particles,crosslinked acrylic resin particles, crosslinked methacrylic resinparticles and silicone particles.

In an embodiment (4) of the present invention, when thetransesterification reaction of a dialkylester of an aromaticdicarboxylic acid with ethylene glycol is carried out in the presence ofthe catalyst system and the polycondensation reaction is carried out toproduce a polyester resin, dimethyl terephthalate recovered bydepolymerizing a polyalkylene terephthalate is used as a portion of 70%by weight or more of the dialkylester of the aromatic dicarboxylic acid.At this time, the catalyst system is preferably used after preparing soas to meet the above-mentioned requirements (a), (b) and (c).

In the embodiment (4), the polyalkylene terephthalate subjected to thedepolymerization is preferably polyethylene terephthalate and, forexample, recovered polyesters such as recovered bottles, recoveredpolyester fiber products, recovered polyester film products and scrappolymers generated in the manufacturing processes of these products areused particularly preferably. In case dimethyl terephthalate obtained bydepolymerizing the polyalkylene terephthalate is used in an amount lessthan 70% by weight, a proportion of the component originating from therecovered dimethyl terephthalate is less than 50% among the componentscontained in the finally obtained polyester or polyester fibers, andthus reducing an impression of environmentally friendly product.Therefore, it is not preferred. The dimethyl terephthalate obtained bydepolymerizing the polyalkylene terephthalate is preferably used in anamount of 80% by weight or more, and more preferably 90% by weight ormore.

The process for producing the dimethyl terephthalate obtained bydepolymerizing the polyalkylene terephthalate used in the presentinvention is not specifically limited and includes, for example,procedures of depolymerizing polyethylene terephthalate with ethyleneglycol, transesterifying with methanol and purifying the resultingdimethyl terephthalate by means of recrystallization or distillation.Among impurities contained in dimethyl terephthalate obtained bydepolymerizing the polyalkylene terephthalate, the content of2-hydroxyterephthalic acid is preferably 2 ppm or less.

The polyester produced by the above procedures can be used to producefibers, films and bottles. Fibers can be produced by the proceduresdescribed in the embodiment (2), and the films can be produced by theprocedures described in the embodiment (3).

In an embodiment (5) of the present invention, a polyethyleneterephthalate film is produced by the process of the present invention.In this embodiment the content of impurities contained in terephthalicacid (TA) used as a starting material is controlled as follows: thecontent of monomethyl terephthalate (MMT) is controlled to 1000 ppm orless and the total content of 4-carboxybenzaldehyde (4-CBA), para-toluicacid (p-TA), benzoic acid (BA) and dimethyl hydroxyterephthalate (HDT)is controlled to 1 ppm or less. Terephthalic acid may be obtained bydepolymerizing a used polyester packaging material by heating in analkylene glycol and hydrolyzing dimethyl terephthalate (DMT) obtained bytransesterifying the depolymerization product with methanol. As thepolycondensation catalyst system, a reaction product of a titaniumalkoxide of the general formula (4) with a phosphorus compound of thegeneral formula (1) in employed. The ratio of the molar amount ofphosphorus atoms to that of titanium atoms in the catalyst is preferably1.0 or more and less than 8.0.

In the embodiment (5), in order to obtain terephthalic acid, whichcontains MMT in a content of 1000 ppm or less, the hydrolysis reactionof DMT is preferably carried out at a temperature within a range from230 to 260° C. under a pressure within a range from 3.0 to 4.6 MPa(gauge pressure), and more preferably at a temperature within a rangefrom 250 to 260° C. under a pressure within a range from 4.0 to 4.6 MPa(gauge pressure), for 2 to 3 hours. MeOH produced during the hydrolysisreaction is removed, together with dimethyl ether produced as aby-product, by introducing stripping steam into a reactor.

TA produced during the hydrolysis reaction is collected by suspending ordissolving in water, discharging it out of the reactor, and subjectingit to a plurality of crystallization treatments and to a solid-liquidseparation procedure. The resulting TA cake can be subjected to drying,grinding and preparing a slurry and then to a esterification reactionand the polycondensation reaction.

The content of MMT in the terephthalic acid obtained by the aboveprocedures is 1000 ppm, while the total content of 4-CBA, p-TA, BA andHDT is 1 ppm or less, and therefore terephthalic acid is suitable for apolyester resin for film.

Since TA contains MMT in an amount of less than 1000 ppm, glycolterminals of polyethylene terephthalate obtained by the polycondensationreaction are blocked and the thermal stability thereof is improved.However, if the content exceeds 1000 ppm, the transparency of theresulting polyethylene terephthalate may be decreased.

In the polyethylene terephthalate resin of the embodiment (5), it ispreferred that the TA component accounts for 85 molar % based on theentire acid component, and the ethylene glycol component accounts for 85molar % based on entire diol component.

The total content of the poly(alkylene aromatic dicarboxylate ester)resin other than polyethylene terephthalate, which may be contained inthe polyethylene terephtalate of the embodiment (5), is 15 molar % orless and the acid component may be selected from aromatic dicarboxylicacid components for example, 2,6-naphthalenedicarboxylic acid,2,7-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid,1,7-naphthalenedicarboxylic acid, other isomers ofnaphthalenedicarboxylic acids, isophthalic acid, diphenyldicarboxylicacid, diphenoxyethanedicarboxylic acid, diphenyletherdicarboxylic acidand diphenylsulfonedicarboxylic acid; alicyclic dicarboxylic acidcomponents, for example, hexahydroterephthalic acid andhexahydroisophthalic acid; aliphatic dicarboxylic acid components, forexample, adipic acid, sebacic acid and azelaic acid; and difunctionalcarboxylic acid components, for example, hydroxycarboxylic acids such asp-β-hydroxyethoxybenzoic acid and ε-oxycaproic acid. The diol componentother than ethylene glycol may be at least one member selected fromtrimethylene glycol, tetramethylene glycol, hexamethylene glycol,decamethylene glycol, neopentyl glycol, diethylene glycol,1,1-cyclohexane dimethanol, 1,4-cyclohexane dimethanol,2,2-bis(4′-β-hydroxyphenyl)propane andbis(4′-β-hydroxyethoxyphenyl)sulfone. Furthermore, a tri- orpoly-functional compound may be copolymerized in the amount of 10% orless.

In the embodiment (5), a drawn polyester film is produced bymelt-extruding the polyester resin obtained by the above procedures andquenching the extruded melt stream to form a undrawn film, and biaxiallydrawing the undrawn film. After drawing, the resulting polyester film isoptionally subjected to a heat set treatment and/or a relaxing heattreatment, if necessary.

In an embodiment (6) of the present invention, a polyester film isproduced from a polyester resin which is produced by the procedures inwhich a used polyester material is subjected to the depolymerizationreaction, the transesterification treatment and the hydrolysistreatment, to prepare an alkyl aromatic dicarboxylate ester containingdimethyl terephthalate in a content of 70% by weight or more; theresultant alkyl aromatic dicarboxylate ester and ethylene glycol aretransesterified in the presence of a portion of the catalyst system; theresultant reaction mixture is added with the remaining portion of thecatalyst system and the ester or oligomer contained in the reactionmixture is polycondensed, to produce the polyester resin. In this case,a mixture of a titanium compound component (1) with a phosphoruscompound component (2a) is used as the catalyst system. The titaniumcompound component (1) is used as the catalyst in thetransesterification reaction, and then the phosphorus compound component(2a) is added for the polycondensation reaction of the resulting esteror an oligomer thereof. The catalyst preferably meets theabove-mentioned requirements (a), (b) and (c). In the resultingpolyester resin, the content of repeating ethylene terephthalate unitsis preferably 80 molar % or more based on the amount of all the esterrepeating units. The dicarboxylic acid component and the diol componentof repeating non-ethylene terephthalate units in the polyester may bethe same as those described in the embodiment (5).

In the procedures of the embodiment (6), dimethyl terephthalate obtainedby depolymerizing the polyalkylene terephthalate is preferably used, asthe dialkylester of the aromatic dicarboxylic acid which is a startingmaterial of the polyester, in the content of 50 molar % or more based ontotal molar amount of the acid component for the polyester.

As the polyalkylene terephthalate, polyethylene terephthalate ispreferred, and recovered polyesters such as recovered PET bottles,recovered polyester fiber products, recovered polyester film productsand scrap polymers generated in the manufacturing processes of theseproducts are used particularly preferably.

In case dimethyl terephthalate obtained by depolymerizing thepolyalkylene terephthalate is used in the content of 70% by mass orless, a proportion of the component originating from the recovereddimethyl terephthalate is less than 50% among the components containedin the polyester obtained finally or polyester fibers, and thus theefficiency of the used polyester products in reuse thereof isinsufficient. The content of dimethyl terephthalate obtained bydepolymerizing the polyalkylene terephthalate is preferably 80% byweight or more, and more preferably 90% by weight or more, based on thetotal amount of the dialkyl aromatic dicarboxylate ester.

When the recycleded dimethyl terephthalate is employed, procedures forproducing the dimethyl terephthalate are not specifically limited. Forexample, in the procedures, polyethylene terephthalate is depolymerizedwith ethylene glycol, the resultant product is transesterified withmethanol and the resulting dimethyl terephthalate is purified by meansof recrystallization or distillation. Among impurities contained indimethyl terephthalate obtained by depolymerizing the polyalkyleneterephthalate, the content of 2-hydroxyterephthalic acid is preferably 2ppm or less.

The intrinsic viscosity of the polyester usable for the polyester filmis not specifically limited. Usually, it is preferably within a rangefrom 0.50 to 0.80, more preferably from 0.55 to 0.75, and particularlypreferably from 0.60 to 0.70. When the intrinsic viscosity is within theabove range, the resulting film has a sufficient mechanical strength andthe polymer for the film is not necessary to have an excessivelyincreased intrinsic viscosity. Therefore, it is economicallyadvantageous.

The process for producing the polyester film is not specifically limitedand the polyester film can be produced by melt-extruding the polyesterresin obtained by the above process and quenching the resin to form aundrawn film, and biaxially drawing the undrawn film. After drawing, theresulting polyester film may be subjected to a heat set treatment and/ora relaxing heat treatment, if necessary.

In an embodiment (7) of the present invention, for the production of apolyester resin having an ethylene terephthalate structures as principalrepeating units, a mixture of a titanium compound component (1) and aphosphorus compound component (2b) comprising at least one memberselected from the phosphorus compound of the general formulae (2) and(3) is used as a catalyst system. A titanium alkoxide usable for thetitanium compound component (1) is preferably selected from the compoundof the general formula (4). The catalyst system usable for theembodiment (7) preferably meets the above-mentioned requirements (a),(b) and (c).

In the embodiment (7), an ester of terephthalic acid with ethyleneglycol, or an oligomer thereof is preferably produced by thetransesterification reaction of the dialkylester of terephthalic acidwith ethylene glycol, and the dialkylester of terephthalic acid ispreferably dimethyl terephthalate. A portion or all of dimethylterephthalate subjected to the transesterification reaction may be oneregenerated from used shaped articles (for example, fibers, films andbottles) of a polyester resin, preferably a polyethylene terephthalateresin.

The polyester film obtained by the procedures of the embodiment (7) canbe used to produce fibers. The polyester for this use preferably has anintrinsic viscosity (o-chlorophenol, 35° C.) within a range from 0.40 to0.80, more preferably from 0.45 to 0.75, and particularly preferablyfrom 0.50 to 0.70. The intrinsic viscosity of less than 0.40 is notpreferred, because the resulting fibers have poor mechanical strength.On the other hand, when the intrinsic viscosity exceeds 0.80, and whenthe resulting polyester is subjected to melt spinning the melt of thepolyester may exhibit an excessively increased viscosity.

When polyester fibers are produced from the polyester resin of theembodiment aspect (7), the fiber-producing procedures used in theembodiment (4) may be utilized.

EXAMPLES

The present invention will be explained by way of the followingExamples.

In the following Examples and Comparative Examples, the resultingpolyester resins, fibers and films were subjected to the followingtests.

1. Intrinsic Viscosity

0.6 g of a polyester was heat-dissolved in 50 ml of ortho-chlorophenoland after cooling to room temperature, the viscosity of the resultingpolyester solution was measured a temperature of 35° C. using an Ostwaldviscometer and the intrinsic viscosity (IV) of the polyester wascalculated from data of the resulting solution viscosity.

2. Color Tone of Polymer (Color Value L and Color Value b)

A sample of a polymer was melted at 290° C. under vacuum for 10 minutes,the melt was formed into a plate having a thickness of 3.0±1.0 mm on analuminum plate, and then immediately quenched in ice water. Theresulting plate was dried at 160° C. for one hour, subjected to acrystallization treatment and then placed on a white standard plate foradjusting a color difference meter. The color value L and the colorvalue b were measured by a Hunter type color difference meter CR-200manufactured by Minolta Co., Ltd. The value L indicates the brightnessand the larger the numerical value, the higher the brightness. Thelarger the value b, the larger the degree of the yellowish tint.

3. Analysis of Metal Content

The concentration of titanium atoms and the concentration of phosphorusatoms in the catalyst were determined in the following manner. In caseof a catalyst solution, the catalyst solution was placed as a sample,into a liquid cell, while in case of being contained in the polyesterresin, a granular polyester sample containing the catalyst was meltedwith heating on an aluminum plate and formed into a formed articlehaving a planar surface using a compression presser. Then, each samplewas quantitatively analyzed by a fluorescent X-ray spectrometer (Model3270E, manufactured by Rigaku Denki Co., Ltd.).

The concentration of titanium atoms in a polymer, to which titaniumoxide was added as a delusterant, was determined in the followingmanner. A sample was dissolved in hexafluoroisopropanol and titaniumoxide particles were sedimentated from the solution using a centrifugalseparator. After recovering only a supernatant liquid by a decantationprocess, the solvent in the recovered supernatant liquid was vaporizedto produce a test sample, which was subjected to the measurement.

4. Diethylene Glycol (DEG) Content

A polymer was decomposed by using hydrazine hydrate and the content ofdiethylene glycol in the decomposition product was measured by gaschromatography (model: 263-70, manufactured by Hitachi, Ltd.).

5. Color Tone of Drawn Film (Color Value L and Color Value b)

Five pieces of a biaxially drawn polyester film were superimposed oneach other and the resulting superimposed pieces were crystallized byheat-treating in a drying machine at 160° C. for 90 minutes. Then, thevalue L and the value b of the film were measured by a color machine,Model CM-7500, manufactured by Color Machine Co., Ltd.

6. Haze

A granular polymer sample was heat-treated and dried in a drying machineat 150° C. for 6 hours, melted with heating at 290° C. in a meltextruder, extruded in the form of a sheet onto a rotary cooling drum andthen rapidly cooled and solidified to produce a undrawn film (sheet)having a thickness of 500 μm. After sampling a portion of the resultantundrawn film free from surface scratch, the Haze value of the sample wasmeasured by a turbidimeter (HDH-1001DP) manufactured by Nippon DenshokuIndustries Co., Ltd.

7. Thermal Stability (Undrawn Film)

A value (A) of the intrinsic viscosity of the sample of an the undrawnfilm prepared for the measurement of Haze and a value (B) of theintrinsic viscosity of a polymer used to produce the undrawn film weredetermined. The thermal stability of the undrawn film to be tested wasevaluated from a difference value (B−A) in accordance with the followingcriteria.

Special class 0–0.05 (particularly excellent thermal stability) Firstclass 0.05–0.10 (excellent thermal stability) Second class 0.10–0.15(good thermal stability) Third class >0.15 (poor thermal stability)8. Thermal Stability (Biaxially Drawn Film)

Five pieces of a biaxially drawn polyester film were superimposed oneach other and the resulting superimposed pieces were crystallized byheat-treating in a drying machine at 160° C. for 90 minutes and a value(A) of the intrinsic viscosity of the resulting biaxially drawn film anda value (B) of the intrinsic viscosity of a polymer used to produce thebiaxially drawn film were determined. The thermal stability wasevaluated from a difference value (B−A) in accordance with the followingcriteria.

Special class 0–0.05 (particularly excellent thermal stability) Firstclass 0.05–0.10 (excellent thermal stability) Second class 0.10–0.15(ordinary thermal stability) Third class >0.15 (poor thermal stability)9. Analysis of Dimethyl Terephthalate(a) Content of Dimethyl 2-Hydroxyterephthalate

Dimethyl terephthalate was dissolved in an acetone solvent and thecontent of dimethyl 2-hydroxyterephthalate in this solution wasdetermined by gas chromatography (Model HP5890, manufactured byHewlett-Packard Company; capillary column DB-17, manufactured by J&WInc.) and then determined by mass spectrometric analysis using GC-MASS(GC/mass spectrometer, Model HP6890/HP5973, manufactured byHewlett-Packard Company; capillary column DB-17, manufactured by J&WInc.).

10. Analysis of Terephthalic Acid

(a) Mass Concentrations of 4-Carboxybenzaldehyde, Paratoluic Acid andHydroxybenzaldehyde

A sample of test terephthalic acid was dissolved in 2N ammonia water andthe resulting solution was subjected to a liquid chromatograph system(LC-6A, STRΦDS-H column) manufactured by Shimadzu Corporation and, afterseparating 4-carboxybenzaldehyde, paratoluic acid andhydroxybenzaldehyde from the solution, the mass concentrations of thecompounds were measured.

(b) Mass Concentration of Monomethyl Terephthalate

A sample of terephthalic acid to be tested was subjected to high speedliquid chromatography (apparatus: Model HPLC D-7000, manufactured byHitachi, Ltd.; packed column: RP-18, 2 columns) and then the massconcentration of monomethyl terephthalate contained in the sample wasmeasured.

(c) Mass Concentration of Benzoic Acid

After a sample of terephthalic acid to be tested was esterified withdiazomethane, the resulting ester was subjected to gas chromatographyusing 10% SE-30 as a separation column and the mass concentration ofbenzoic acid contained in the sample was measured by using n-tridecaneas an internal standard.

11. Layers of Deposit Formed Around Spinneret

After a polyester to be tested was formed into chips, the resultingchips were melted at 290° C., and the melt was extruded through aspinneret having 12 spinning orifices each having a hole diameter of0.15 mmΦ, and the melt-spinning was continuously carried out at aspinning speed of 600 m/min for 2 days. Then, a height of each layer ofa deposit formed on the outer peripheries of a spinning orifices of thespinneret was measured. A bending of filamentary stream of the extrudedpolyester melt is promoted with increase in the height of the depositlayer formed around the outer edge of the spinning orifice, and theformability of the polyester becomes poor. That is, the height of thedeposit layer formed around the spinning orifice is an index of theformability of the polyester.

12. Tensile Strength and Ultimate Elongation of Fibers

The tensile strength and the ultimate elongation of fibers were measuredin accordance with the procedure described in JIS L 1013.

Production Example 1

Synthesis of Titanium Trimellitate

To an ethylene glycol solution prepared by mixing 2 parts by mass oftrimellitic anhydride with 98 parts by mass of ethylene glycol,tetrabutoxytitanium was added in an amount enough to control a molarratio thereof to trimellitic anhydride to 0.5, and then the resultingmixture was reacted by maintaining in an air at a temperature of 80° C.under the ambient atmospheric pressure for 60 minutes. After cooling itto room temperature, the product was subjected to recrystallization fromacetone in an amount of 10 times that of the product and, the resultantdeposit was collected by filtering through a filter paper and dried at100° C. for 2 hours, to prepare the target titanium compound.

Example 1

A mixture of 100 parts by mass of dimethyl teraphthalate with 70 partsby mass of ethylene glycol was admixed with 0.009 parts by mass oftetra-n-butyl titanate in an SUS (stainless steel) vessel in which areaction under pressure can be carried out and the resulting admixturewas subjected to transesterification in the vessel by increasing thetemperature from 140° C. to 240° C. under a pressure of 0.07 MPa. Then,0.04 parts by mass of triethyl phosphonoacetate was added to thereaction mixture, to complete the transesterification reaction.

The reaction product was placed in a polymerization vessel and thensubjected to a polycondensation reaction by heating it to a temperatureof 290° C. under high vacuum of 26.7 Pa (0.2 mmHg) or less to produce apolyethylene terephthalate resin which has an intrinsic viscosity of0.60 and contains diethylene glycol in a content of 1.5% by mass (basedon the molar amount of an ethylene terephthalate component).

The polyethylene terephthalate resin was continuously extruded in theform of filamentary streams through a extruding orifices of amelt-spinning apparatus, and then the filamentary streams were cooledand cut into granular pellets each having a length of about 3 mm. Theresulting pellets were dried at 180° C. for 3 hours and then subjectedto a melt spinning procedure to produce an undrawn filament yarn havinga yarn count of 333 dtex/36 fil. Then, the undrawn filament yarn wasdrawn at a draw ratio of 4.0, to provide a drawn multi-filament yarnhaving a yarn count of 83.25 dtex/36 fil.

Separately the same dry pellets as mentioned above were fed in asingle-screw kneading extruder (inner diameter: 65 mm, path length: 1000mm, residence time: 10 minutes), melt-kneaded while gradually raisingthe temperature of the feed in the extruder from 280° C. to 300° C., andthen the polyester melt was extruded through a die to produce a undrawnfilm. The resulting undrawn film was biaxially drawn at 90° C. at alongitudinal draw ratio of 3.5 and a transverse draw ratio of 4.0, andthen heat set at 200° C., to produce a film having a thickness of 15 μm.

Example 2

A polyester resin was produced in the same manner as in Example 1,except that the polycondensation reaction was carried out using 0.016parts by mass of titanium trimellitate synthesized in Production Example1 as a titanium compound. The properties of the resulting polyestercomposition fibers and undrawn film produced by using the polyestercomposition are shown in Table 1.

Examples 3 to 9 and Comparative Examples 1 to 7

In each of Examples 3 to 9 and Comparative Examples 1 to 7, a polyesterresin composition was produced by the same procedures as in Example 1,except that the types and amounts of the titanium compound and thephosphorus compound were changed as shown in Table 1. The properties ofthe resulting polyester resins and the undrawn film obtained by usingthe same are shown in Table 1.

Comparative Example 8

A mixture of 100 parts by mass of dimethyl teraphthalate and 70 parts bymass of ethylene glycol was admixed with 0.009 parts by mass oftetra-n-butyl titanate in an SUS (stainless steel) vessel in which areaction under a pressure can be carried out and the resulting mixturewas subjected to a transesterification reaction by heating it from 140°C. to 240° C. under a pressure of 0.07 MPa. Then, 0.04 parts by mass oftriethyl phosphonoacetate was added to the reaction admixture, tocomplete the transesterification reaction.

After 0.053 parts by mass of diantimony trixoide was added to theresultant reaction mixture, the mixture was placed in a polymerizationvessel and then subjected to a polycondensation reaction by heating itto 290° C. under high vacuum of 26.67 Pa (0.2 mmHg) or less, to producea polyester resin which had an intrinsic viscosity of 0.60 and containeddiethylene glycol in a content of 1.5% by mass.

Example 10

A polyester resin was produced and then fibers were produced by sameprocedures as in Example 1, except that the amounts of the titaniumcompound and the phosphorus compound were changed as shown in Table 1and, after the completion of the transesterification reaction, 20% bymass of titanium oxide having an average particle size of 0.3 μm and 1.5parts by mass of an ethylene glycol slurry were added to the resultantreaction mixture. The measurement results are shown in Table 1.

Example 11

The same procedures as in Example 1 were carried out to produce-apolyester resin and fibers, except that the amounts of the titaniumcompound and the phosphorus compound were changed as shown in Table 1and, after the completion of the transesterification reaction, 0.02parts by mass ofpentaerythritol-tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate](manufactured by Ciba Speciality Chemicals Inc., under the trademark ofIrganox 1010) was added to the resultant reaction mixture. Themeasurement results are shown in Table 1.

Example 12

A slurry prepared by mixing 200 parts by mass of terephthalic acid with105 parts by mass of ethylene glycol was charged in a reactor equippedwith a stirrer, a rectifying column and a water distillation condenser.Then, the slurry was subjected to an esterification reaction at 270° C.under a pressure of 0.3 MPa for 240 minutes. After a half portion of theresulting reaction mixture was removed, the residual half portion of thereaction mixture was maintained at a temperature of 250° C. and 100parts by mass of terephthalic acid, and 52 parts by mass of an ethyleneglycol slurry were fed into the reaction system under the ambientatmospheric pressure over 150 minutes. Then, the esterification reactionwas carried out under the ambient atmospheric pressure over 90 minutes.During the reaction, the temperature of the reaction system wasmaintained at 250° C.

After the half portion of the resulting reaction product was removed,100 parts by mass of terephthalic acid and 52 parts by mass of anethylene glycol slurry were fed and the esterification reaction wascarried out, and then these procedures were repeated until the contentof diethylene glycol in the reaction product is stabilized.

After the content of diethylene glycol in the reaction product wasstabilized, a half portion of the reaction product mixture obtained bythe esterification reaction was transferred to a polycondensationreaction apparatus and 0.018 parts by mass of the titanium catalystproduced in Preliminary Example 1 and 0.040 parts by mass of triethylphosphate were added thereinto. Then, the polycondensation reaction wascarried out by heating the mixture to 285° C. under high vacuum of 26.67Pa or less to produce a polyester which had an intrinsic viscosity of0.62 and contained diethylene glycol in a content of 1.0% by mass, andfibers were produced by using the polyester by the same procedure as inExample 1. The measurement results are shown in Table 1.

TABLE 1 Polyester polymer Sb Titanium compound Phosphorus compound Molarcompound Titanium Content Content ratio M_(Ti) + (Sb₂O₃) oxide (% Colortone Kind (mmol %) Kind (mmol %) M_(p)/M_(Ti) M_(p) mmol % by mass)Antioxidant IV Value L Value b Example 1 TBT 5 TEPA 30 6 35 — — — 0.62079.0 3.0 Example 2 TNT 5 TEPA 30 6 35 — — — 0.620 80.0 2.8 Example 3 TNT5 PEE 30 6 35 — — — 0.620 78.0 3.0 Example 4 TNT 5 HPE 30 6 35 — — —0.620 78.0 3.0 Example 5 TNT 3 TEPA 15 5 18 — — — 0.600 80.0 2.3 Example6 TNT 7 TEPA 50 7 57 — — — 0.600 80.0 3.3 Example 7 TNT 5Orthophosphoric 30 6 35 — — — 0.600 76.0 4.3 acid Example 8 TNT 5 TMP 306 35 — — — 0.600 77.0 4.0 Example 9 Titanium 5 TEPA 30 6 35 — — — 0.60078.0 4.5 oxide Example 10 TNT 5 TEPA 30 6 35 — 0.3 — 0.620 75.5 7.5Example 11 TNT 5 TEPA 30 6 35 — — 200 0.620 80.5 2.0 Example 12 TNT 6TEPA 30 6 35 — — — 0.620 82.1 0.3 Comparative TNT 15 TEPA 45 3 60 — — —0.640 77.0 12.0 Example 1 Comparative TNT 25 TEPA 50 3 75 — — — 0.64077.0 12.0 Example 2 Comparative TNT 1.5 TEPA 10 6.7 11.5 — — — 0.45083.0 −1.0 Example 3 Comparative TNT 5 TEPA 7 1.4 12 — — — 0.640 77.011.0 Example 4 Comparative TNT 5 TEPA 90 18 95 — — — 0.520 83.0 0.0Example 5 Comparative TNT 9 TEPA 100 11.1 109 — — — 0.600 78.0 3.0Example 6 Comparative TNT 2 TEPA 7 3.5 9 — — — 0.600 80.0 2.0 Example 7Comparative TBT 5 TEPA 30 6 35 31 — — 0.640 70.0 2.5 Example 8Properties of fibers Properties of non-stretched film Height ofspinneret Haze value Thermal stability Tensile strength (cN/dtex)Ultimate elongation (%) foreign matters (μm) Example 1 0.2 0.02 3.7 27 3Example 2 0.2 0.02 3.8 26 4 Example 3 0.2 0.02 3.8 28 4 Example 4 0.20.02 Example 5 0.2 0.01 3.6 27 2 Example 6 0.2 0.02 3.7 25 4 Example 70.3 0.05 Example 8 0.3 0.04 3.6 26 3 Example 9 0.2 0.03 3.6 29 4 Example10 3.8 27 3 Example 11 3.8 26 4 Example 12 3.7 27 3 Comparative 0.3 0.07Example 1 Comparative 3.8 26 5 Example 2 Comparative impossible to formfilm 3.0 23 2 Example 3 Comparative 0.2 0.03 3.9 28 3 Example 4Comparative impossible to form film 3.2 22 4 Example 5 Comparative 0.90.09 3.7 29 4 Example 6 Comparative impossible to form film 3.6 27 3Example 7 Comparative 1   0.04 3.9 28 50  Example 8

Production Example 2 Synthesis of Catalyst

In a 2 liter three-necked flask equipped with a function capable ofmixing a solution with stirring, 808 g of ethylene glycol and 50 g ofacetic acid were charged and mixed with each other by stirring, and then142 g of titanium tetrabutoxide was slowly added to the mixture, toprovide a transparent ethylene glycol solution of a titanium compound.The resulting solution is referred to as a “TB solution”. The titaniumconcentration of the TB solution was measured using fluorescent X-rays.As a result, the Ti concentration was 2.0%.

Further, in a 2 liter three-necked flask equipped with a functioncapable of mixing a solution with stirring, 896 g of ethylene glycol wascharged and 224 g of triethyl phosphonoacetate was added thereto whilestirring to provide a transparent solution. This solution is referred toas a “TP1 solution”.

Subsequently, the TP1 solution was heated, the temperature of thesolution was controlled to 160° C., and 400 g of the previously preparedTB solution was gradually added to the TP1 solution. After adding thetotal amount of the TB solution, stirring was continued at a temperatureof 160° C. for one hour, thereby completing the reaction of the titaniumcompound component with the phosphorus compound component. At this time,a ratio of the amount of the TP1 solution to that of the Tb solution wascontrolled to 6.0 in terms of a ratio of a molar concentration ofphosphorus atoms to titanium atoms. The reaction product is a solutionwhich is soluble in ethylene glycol and has a pale yellowish tint. Theresulting solution is referred to as a “TT-6 catalyst”.

Production Example 3

A catalyst was produced by using the same apparatus and procedure asthose in Production Example 2, except that the prepared amount and addedamount of the TP1 solution described in Production Example 2 werechanged as described hereinafter. In basically the same reactor asmentioned above, 1045 g of ethylene glycol was charged and 75 g ofethylene glycol was added thereto while stirring to provide atransparent solution. This solution is referred to as a “TP2 solution”.Subsequently, the TP2 solution was heated to control the temperature ofthe solution to 120° C. and 400 g of the previously prepared TB solutionwas gradually added thereto while stirring the mixture. After adding thetotal amount of the TB solution, stirring was continued at a temperatureof 120° C. for 3 hours, thereby completing the reaction of the titaniumcompound component with the phosphorus compound component. At this time,a ratio of the amount of the P1 solution to that of the Tb solution wascontrolled to 2.0 in terms of a ratio of a molar concentration ofphosphorus atoms to titanium atoms. As a result, a transparent solutionwas obtained. The resulting solution is referred to as a “TT-2solution”.

Example 13

In a reactor containing 225 parts of an oligomer of an ethylene glycolterephthalate ester, a slurry prepared by mixing 179 parts of highpurity terephthalic acid with 95 parts of ethylene glycol was fed at auniform feed rate while stirring under the conditions in a nitrogenatmosphere at 255° C. under the ambient atmospheric pressure, and thenthe esterification reaction was continued for 4 hours while distillingoff water and ethylene glycol produced during the reaction out of thesystem, thereby completing the reaction. At this time, the degree ofesterification was 98% or more and the degree of polymerization of theresulting oligomer was about 5 to 7.

225 parts of the oligomer obtained by the esterification reaction wastransferred to a polycondensation reactor and the oligomer was mixedwith 0.182 parts of the titanium-phosphorus reaction product TT-6catalyst solution described in Production Example 2 as apolycondensation catalyst. Subsequently, the reaction temperature in thesystem was increased from 255° C. to 290° C. and the reaction pressurewas reduced stepwise from atmospheric pressure to 60 Pa, and then thepolycondensation reaction was carried out while removing water andethylene glycol produced during the reaction out of the reaction system.

The proceeding degree of the polycondensation reaction was detectedwhile monitoring the load on a stirring blade in the system and thereaction was completed upon reaching a desired polymerization degree. Atthis time, the polycondensation reaction time was 160 minutes. Then, thereaction product in the system was continuously extruded into a strandform through a extruding orifice of a melt sipping apparatus, and thenthe strand-formed stream was cooled and cut to provide granular pelletseach having a length of about 3 mm. The resulting pellets were dried at180° C. for 3 hours and then fed in a single-screw kneading extruder(inner diameter: 65 mm, path length: 1000 mm, residence time: 10minutes), melt-kneaded while gradually increasing a temperature in theextruder from 280° C. to 300° C., and then the molten polyester wasextruded through a die to produce an undrawn film. The resulting undrawnfilm was biaxially drawn at 90° C. in a longitudinal draw ratio of 3.5times and a transverse draw ratio of 4.0 times, and then heat set at200° C. to produce a film having a thickness of 15 μm.

Example 14

A polycondensation reaction was carried out and a film was produced bythe same procedures as in Example 13, except that the polycondensationcatalyst was replaced by the titanium-phosphorus reaction compound TT-2solution prepared in Production Example 3. At this case, thepolycondensation reaction time was 135 minutes.

The properties of the resulting polyester granular pellets and thepolyester film are shown in Table 2.

Example 15

A polycondensation reaction was carried out and a polyester film wasproduced by the same procedures as in Example 13, except that tetrazoleblue (abbreviated to an agent B) as a color-regulating agent was addedin an amount of 0.3 ppm based on the amount of the target polymer, inaddition to the titanium-phosphorus reaction compound TT-6 solutionprepared in Production Example 2. In this case, the polycondensationreaction time was 160 minutes.

The properties of the resulting polyester granular pellets and thepolyester film are shown in Table 2.

Example 16

A polycondensation reaction was carried out and a film was produced bythe same procedures as in Example 13, except that 0.129 parts of the TBsolution and 0.372 parts of the TP1 solution each prepared in ReferenceExample 2 were separately mixed as the polycondensation catalyst intothe reaction system without reacting the TB solution with the TP1solution. In this case, the polycondensation reaction time was 190minutes. The properties of the resulting polyester granular pellets andthe polyester film are shown in Table 2.

Comparative Example 9

A polycondensation reaction was carried out and a film was produced bythe same procedures as in Example 13, except that the amount of TT-2 waschanged to 0.546 parts. In this case, the polycondensation reaction timewas 135 minutes.

The properties of the resulting polyester granular pellets and thepolyester film are shown in Table 2.

Comparative Example 10

A Spolycondensation reaction was carried out and a film was produced bythe same procedures as in Example 13, except that the polycondensationcatalyst was replaced by an ethylene glycol solution having aconcentration of 1.3% of antimony trioxide and the amount of thecatalyst was changed to 4.83 parts and, moreover, 0.121 parts of a 25%ethylene glycol solution of trimethyl phosphate as a stabilizer wasadded. In this case, the polycondensation reaction time was 130 minutes.

The properties of the resulting polyester granular pellets and thepolyester film are shown in Table 2.

Comparative Example 11

A polycondensation reaction was carried out and a film was produced bythe same procedures as in Example 13, except that the polycondensationcatalyst was replaced by the TB solution prepared in Production Example2 and the amount of the catalyst was changed to 0.129 parts. In thiscase, the polycondensation reaction time was 105 minutes.

The properties of the resulting polyester granular pellets and thepolyester film are shown in Table 2.

TABLE 2 Polyester polymer Properties of film Sb After stretchingcompound Color tone Color Species of M_(Ti) + M_(p) (Sb₂O₃) Value ValueHaze before Value Value Thermal catalyst M_(p)/M_(Ti) (mmol %) (mmol %)IV L b stretching (%) IV L b stability Example 13 TT-6 5.6 33 — 0.62079.0 2.7 0.1 0.580 80.0 3.7 0.03 Example 14 TT-2 1.8 14 — 0.620 81.0 2.50.2 0.580 80.0 3.4 0.04 Example 15 TT-6 5.6 33 — 0.520 78.0 1.4 0.20.580 78.0 2.8 0.04 Example 16 TB solution + TP1 5.2 31 — 0.620 80.0 4.00.6 0.540 82.0 5.5 0.04 solution Comparative TT-2 1.93 44 — 0.620 81.04.1 0.5 0.550 82.0 5.5 0.07 Example 9 Comparative Sb₂O₃ — — 38 0.62072.0 5.0 1.0 0.570 70.0 6.0 0.04 Example 10 Comparative TB solution — 15— 0.630 82.0 7.5 0.3 0.520 83.0 11.0 0.14 Example 11

Production Example 4

Production of Recovered Dimethyl Terephthalate

200 Parts by mass of ethylene glycol was charged in a 500 ml separableflask and 1.5 parts by mass of sodium carbonate and 50 parts by mass ofa polyethylene terephthalate scrap made of ground bottles were furthercharged into the flask, and then the temperature was increased to 185°C. while stirring. This conditions were kept for 4 hours. As a result,the polyethylene terephthalate scrap was dissolved and thedepolymerization reaction was completed. The resulting depolymerizationreaction product was concentrated by a vacuum distillation and, 150parts by mass of ethylene glycol was recovered as a distillate fraction.

Into the concentrated solution, 0.5 Parts by mass of sodium carbonate asa transesterification catalyst and 100 parts by mass of methanol weremixed, and then the reaction mixture was stirred at a liquid temperatureof 75° C. under the ambient atmospheric pressure for one hour, to effectan esterification reaction.

The resulting reaction mixture was cooled to 40° C. and then filteredthrough a glass filter. Crude dimethyl terephthalate recovered on thefilter was mixed with 100 parts by mass of MeOH and the mixture washeated to 40° C., stirred, washed and then filtered again through theglass filter. These washing and filtration procedures were repeatedtwice.

The crude dimethyl terephthalate collected on the filter was charged ina distillation apparatus and subjected to vacuum distillation under theconditions of a pressure of 6.65 kPa and a reflux ratio of 0.5, therebyto recover dimethyl terephthalate as a distillate fraction. The amountof the recovered fraction was 47 parts by mass. The amount of theresidue in the distillation apparatus was measured and the amount ofdimethyl terephthalate was measured. As a result, the dimethylterephthalte was in an amount of 2 parts by mass. The degree of reactionof dimethyl terephthalate was 93% by mass based on the mass of thepolyester charged.

In the recovered dimethyl terephthalate purified by the distillation,0.5 ppm by mass of dimethyl 2-hydroxyterephthalate was detected.

The purified recovered dimethyl terephthalate exhibited a degree ofpurity of 99.9% by weight or more.

Example 17

A mixture of 100 parts by mass of dimethyl terephthalate prepared inProduction Example 4 and 70 parts by mass of ethylene glycol was mixedwith 0.0088 parts by mass of tetra-n-butyl titanate in a stainless steelvessel capable of carrying out a reaction under pressure and theresulting mixture was subjected to a transesterification reaction byheating it from 140° C. to 240° C. under a pressure of 0.07 MPa. Then,0.035 parts by mass of triethyl phosphonoacetate was added to thereaction mixture, thereby completing the transesterification reaction.

The reaction product was transferred to a polymerization vessel and thenpolycondensation reaction was carried out by heating it to 285° C. underhigh vacuum of 26.67 Pa or less to produce a polyester which had anintrinsic viscosity of 0.63 and contained diethylene glycol in a contentof 1.0% by mass.

The resulting ester was formed into chips using a melt extruder and thendried at 180° C. Using the resulting dry chips, an undrawn filament yarnhaving a yarn count of 333 dtex/36 filaments was produced by a meltspinning procedure and then the undrawn filament yarn was drawn at adraw ratio of 4.0 to provide a drawn multi-filament yarn having a yarncount of 83.25 dtex/36 filaments. Separately, the dry chips weremelt-extruded using a film forming apparatus to provide an undrawn film,which was biaxially drawn at 90° C. at a longitudinal draw ratio of 3.5and a transverse draw ratio of 4.0, and then heat set at 200° C. toproduce a film having a thickness of 15 μm. The measurement results areshown in Table 3.

Example 18

A polyester resin was produced and polyester fibers were produced fromthe polyester resin by the same procedures as in Example 17, except thatthe 0.016 parts by mass of titanium trimellitate synthesized by theprocedures of Production Example 1 was used as the titanium compound.The measurement results are shown in Table 3.

Examples 19 to 22 and Comparative Examples 12 to 15

In each of Examples 19 to 22 and Comparative Examples 12 to 15, apolyester resin composition and fibers were produced by the sameprocedures as in Example 17, except that the compounds shown in Table 3were used as the titanium compound and the phosphorus compound and theamounts were changed as shown in Table 3. The measurement results areshown in Table 3. In each of Comparative Examples 13 and 15, since thepolycondensation reaction rate is very low, the polycondensationreaction procedure was ended 200 minutes after the start of thereaction.

Comparative Example 16

A mixture of 100 parts by mass of recovered dimethyl teraphthalateprepared in Production Example 4 and 70 parts by mass of ethyleneglycol, was mixed with 0.009 parts by mass of tetra-n-butyl titanate.The resultant mixture was charged in a stainless steel vessel capable ofcarrying out a reaction under pressure and the resulting mixture wassubjected to a transesterification reaction, while heating it from 140°C. to 240° C. under a pressure of 0.07 MPa. Then, 0.04 parts by mass oftriethyl phosphonoacetate was added to the reaction mixture, therebycompleting the transesterification reaction.

After 0.053 parts by mass of diantimony trixoide was added to thereaction mixture, the mixture was transferred to a polymerization vesseland then polycondensation reaction was carried out by heating it to 285°C. under high vacuum of 26.67 Pa or less to prepare a polyester whichhad an intrinsic viscosity of 0.63 and contained diethylene glycol in acontent of 0.9% by mass. In the same manner as in Example 17, theresulting polyester was formed into fibers and a film. The measurementresults are shown in Table 3.

TABLE 3 Polyester polymer Titanium Phosphorus Sb compound compoundcompound Color tone Content Content M_(Ti) + M_(p) (Sb₂O₃) DEG ValueValue Kind (mmol %) Kind (mmol %) M_(p)/M_(Ti) (mmol %) (mmol %) (% bymass) IV L b Example 17 TBT 5 TEPA 30 6 35 — 1.0 0.620 79.0 3.2 Example18 TNT 5 TEPA 30 6 35 — 1.0 0.630 80.2 2.8 Example 19 TNT 5 PEE 30 6 35— 1.0 0.630 78.2 3.1 Example 21 TNT 3 TEPA 15 5 18 — 1.0 0.630 80.3 2.2Example 22 TNT 7 TEPA 50 7 57 — 1.0 0.630 79.7 3.2 Comparative TNT 25 503 75 — 1.1 0.630 75.2 14.3 Example 12 Comparative TNT 1.5 TEPA 10 6.711.5 — 1.0 0.450 83.1 −1.0 Example 13 Comparative 5 TEPA 5 1 12 — 1.00.630 77.2 13.1 Example 14 Comparative TNT 5 TEPA 100 20 105 — 1.1 0.51082.1 −0.4 Example 15 Comparative TBT 5 TEPA 30 6 35 31 0.9 0.630 70.32.4 Example 16 Properties of film Properties of yarn Haze before AfterUltimate Height of spinneret stretching biaxial stretching Tensilestrength elongation foreign matters (%) IV Thermal stability (cN/dtex)(%) (μm) Example 17 0.2 0.580 0.04 3.7 27 3 Example 18 0.1 0.590 0.043.7 25 3 Example 19 0.1 0.590 0.04 3.8 26 2 Example 21 0.1 0.590 0.043.6 26 3 Example 22 0.2 0.570 0.06 3.8 25 3 Comparative 0.8 0.550 0.083.7 27 5 Example 12 Comparative impossible to perform film-formingoperation 3.1 23 3 Example 13 Comparative 0.1 0.570 0.06 3.8 26 2Example 14 Comparative impossible to perform film-forming operation 3.123 3 Example 15 Comparative 1   0.590 0.04 3.9 29 50  Example 16

Example 23

DMT was prepared by depolymerizing PET with ethylene glycol andtransesterifying the resultant EMT with MeOH and further hydrolyzed toprovide TA (in which the sum of 4-CBA, p-TA, BA and HDT is 1 ppm or lessand MMT content is 150 ppm). Previously, in a polycondensation reactorcontaining 225 parts of an oligomer of an ethylene glycol ester ofterephthalic acid, a slurry prepared by mixing 179 parts of therecovered TA with 95 parts of ethylene glycol was fed at a uniform feedrate while stirring the mixture in a nitrogen gas atmosphere at 255° C.under the ambient atmospheric pressure, and then the mixture wassubjected to an esterification reaction at 275° C. under atmosphericpressure for 4 hours, while distilling off water and ethylene glycolproduced during the reaction out of the system until the degree ofesterification reaches 98% or more, to produce an oligomer having adegree of polymerization of about 5 to 7.

A portion of the oligomer prepared by the above-mentioned esterificationreaction was transferred in an amount of 225 parts by mass to apolycondensation reactor and mixed with 0.45 parts of the “TT-6 catalystsolution” prepared in Production Example 2, as a polycondensationcatalyst. Subsequently, the reaction temperature in the reaction systemwas increased from 255° C. to 290° C. and the reaction pressure wasreduced stepwise from the atmospheric pressure, to 60 Pa and then themixture was subjected to a polycondensation reaction, during thereaction water and ethylene glycol produced from the reaction wereremoved out of the system.

The degree of the polycondensation reaction and the load on a stirringblade in the system were detected by monitoring them and the reactionwas completed upon reaching a desired degree of polymerization degree.In this case, the polycondensation reaction time was 160 minutes. Then,the reaction product in the system was continuously extruded into astrand form stream through an extruding orifice of a solution extrudingapparatus, and then the strand-formed stream was cooled and cut toprovide granular pellets each having a length of about 3 mm.

The resulting pellets were dried at 180° C. and then formed into a sheetby subjecting it to a melt film-forming procedure, and then resultingsheet was biaxially drawn at 90° C. in a longitudinal draw ratio of 3.5and a transverse draw ratio of 4.0, and then heat set at 200° C. toproduce a film having a thickness of 15 μm.

The properties of the resulting polyester granular pellets and thepolyester film are shown in Table 4.

Example 24

A polyester resin was produced and a polyester film was produced, thesame procedures as in Example 23, by except that the “TT-2 catalystsolution” prepared in Production Example 3 was used as thepolycondensation catalyst in place of the “TT-6 catalyst solution”. Inthis case, the polycondensation reaction time was 135 minutes. Theproperties of the resulting polyester granular pellets and the polyesterfilm are shown in Table 4.

Example 25

A polyester resin and a polyester film were produced by the sameprocedures as in Example 23, except that the amount of the “TT-2catalyst solution” was changed to 1.50 parts. In this case, thepolycondensation reaction time was 135 minutes. The properties of theresulting polyester granular pellets and the polyester film are shown inTable 4.

Example 26

A polyester resin and a polyester film were produced in the sameprocedures as in Example 23, except that 0.13 parts of the “TB solution”and 0.39 parts of the “TP1 solution” prepared in Production Example 2were separately mixed as the polycondensation catalyst into the reactionsystem without reacting the “TB solution” with the “TP1 solution”. Inthis case, the polycondensation reaction time was 190 minutes. Theproperties of the resulting polyester granular pellets and the polyesterfilm are shown in Table 4.

TABLE 4 Polyester polymer Properties of film Sb After stretchingcompound Color tone Color Species of M_(Ti) + M_(p) (Sb₂O₃) Value ValueHaze before Value Value Thermal catalyst M_(p)/M_(Ti) (mmol %) (mmol %)IV L b stretching (%) IV L b stability Example TT-6 5.6 33 — 0.620 79.03.2 0.1 0.580 80.0 3.7 0.04 23 Example TT-2 1.8 14 — 0.620 81.0 3.9 0.20.580 80.0 4.4 0.03 24 Example TT-6 1.9 44 — 0.520 81.0 7.1 0.5 0.55083.0 9.5 0.07 25 Example TB solution + TP1 5.2 31 — 0.620 81.0 5.0 0.60.540 82.0 5.9 0.04 26 solution

Example 27

A mixture of 100 parts by mass of dimethyl terephthalate and 70 parts bymass of ethylene glycol, and 0.009 parts by mass of tetra-n-butyltitanate were charged in a SUS vessel usable for a reaction underpressure and the resulting mixture was subjected to atransesterification reaction while heating it from 140° C. to 240° C.under a pressure of 0.07 MPa. Then, 0.031 parts by mass of mono-n-butylphosphate was added to the reaction mixture, to thereby complete thetransesterification reaction.

The reaction product was transferred to a polymerization vessel and thensubjected to a polycondensation reaction heating it to 290° C. underhigh vacuum of 30 Pa or less to produce a polyester resin which had anintrinsic viscosity of 0.63 and contained diethylene glycol in a contentof 1.3% by mass.

The resulting polyester resin was formed into chips by a melt granulatorand then dried. The resulting dry chips were subjected to a meltspinning procedure to provide a undrawn filament yarn having a yarncount of 333 dtex/36 filament. Then, the undrawn filament yarn was drawnat a draw ratio of 4.0 to obtain a drawn multi-filament yarn having ayarn count of 83.25 dtex/36 filaments.

The measurement results are shown in Table 5.

Example 28

A polyester resin and polyester fibers were produced by the sameprocedures as in Example 27, except that the titanium compound wasreplaced by 0.016 parts by mass of titanium trimellitate synthesized inProduction Example 5. The measurement results are shown in Table 5.

Examples 29 to 33 and Comparative Examples 17 to 22

In each of Examples 29 to 33 and Comparative Examples 17 to 22, apolyester resin and polyester fibers were produced by the sameprocedures as in Example 27, except that each of the compounds shown inTable 5 were used as a titanium compound or a phosphorous compound ineach amount shown in Table 7. The measurement results are shown in Table5.

Example 34

A polyester resin and polyester fibers were produced by the sameprocedures as in Example 27, except that the titanium compound and thephosphorus compound were replaced by the compounds shown in Table 7which were used in the amounts shown in Table 5 and, after thecompletion of the transesterification reaction, 1.5 parts by mass of anethylene glycol slurry of 20% by mass of titanium oxide was added. Themeasurement results are shown in Table 5.

Example 35

A polyester resin and polyester fibers were produced by the sameprocedures as in Example 27, except that, after the completion of thetransesterification reaction, 0.02 parts by mass ofpentaerythritol-tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate](manufactured by Ciba Speciality Chemicals Inc. under the trademark ofIrganox 1010) was added to the resulting reaction product. Themeasurement results are shown in Table 5.

Comparative Example 23

A mixture of 100 parts by mass of dimethyl terephthalate and 70 parts bymass of ethylene glycol, and 0.009 parts by mass of tetra-n-butyltitanate were charged in a SUS vessel usable for a reaction underpressure and the resulting mixture was subjected to atransesterification reaction while heating it from 140° C. to 240° C.under a pressure of 0.07 MPa. Then, 0.031 parts by mass of mono-n-butylphosphate was added to the reaction mixture, to thereby complete thetransesterification reaction.

After 0.053 parts by mass of diantimony trixoide was added to thereaction mixture, the mixture was transferred to a polymerization vesseland then subjected to a polycondensation reaction by heating to 290° C.under high vacuum of 30 Pa or less to provide a polyester which had anintrinsic viscosity of 0.63 and contained diethylene glycol in a contentof 1.3% by mass. The resulting polyester resin was subjected to the samemelt spinning and drawing procedures as in Example 27 to producepolyester filament yarn. The measurement results are shown in Table 5.

TABLE 5 Titanium Phosphorus compound compound Sb compound TitaniumContent Content (Sb₂O₃) M_(Ti) + M_(p) oxide Antioxidant Kind (mmol %)Kind (mmol %) (mmol %) M_(p)/M_(Ti) (mmol %) (% by mass) (ppm) Example27 TBT 5 NBP 30 — 6 35 — — Example 28 TNT 5 NBP 30 — 6 35 — — Example 29TNT 7 NBP 30 — 4.3 37 — — Example 30 TNT 5 NBP 20 — 4 25 — — Example 31TNT 7 NBP 40 — 5.7 47 — — Example 32 TNT 5 PPA 30 — 6 35 — — Example 33TNT 5 THEP 30 — 6 35 — — Example 34 TNT 5 NBP 20 — 4 25 0.3 — Example 35TNT 5 NBP 30 — 6 35 — 200 Comparative TNT 20 NBP 50 — 2.5 70 — — Example17 Comparative TNT 1.5 NBP 10 — 6.7 11.5 — — Example 18 Comparative TNT5 NBP 5 — 1 10 — — Example 19 Comparative TNT 5 NBP 90 — 18 95 — —Example 20 Comparative TNT 7 NBP 100 — 14.3 107 — — Example 21Comparative TNT 2 NBP 6 — 3.5 8 — — Example 22 Comparative TBT 5 NBP 3031 6 35 — — Example 23 Properties of yarn DEG Tensile Ultimate Height of(% by Color tone strength Intrinsic elongation spinneret foreign IVmass) L b (cN/dtex) viscosity (%) matters (μm) Example 27 0.63 1.3 80 33.8 0.611 28 2 Example 28 0.63 1.3 79.5 2.8 3.8 0.612 27 1 Example 290.63 1.4 79 3 3.7 0.61 28 2 Example 30 0.63 1.3 79.5 2.3 3.6 0.613 27 1Example 31 0.63 1.4 79 3.3 3.7 0.608 26 3 Example 32 0.63 1.3 80 4 3.80.611 29 2 Example 33 0.63 1.3 79.5 4.5 3.7 0.612 27 2 Example 34 0.631.1 75 7.5 3.7 0.611 28 1 Example 35 0.63 1.3 80.2 2 3.8 0.62 26 3Comparative 0.63 1.7 77 13 3.9 0.607 26 4 Example 17 Comparative 0.450.9 82 1 3 0.44 22 1 Example 18 Comparative 0.63 1.3 77 11 3.9 0.608 282 Example 19 Comparative 0.51 1.3 81 1 3.2 0.498 22 2 Example 20Comparative 0.54 1.4 78 2 3.1 0.529 23 3 Example 21 Comparative 0.52 0.980 2 3.2 0.505 22 1 Example 22 Comparative 0.63 1.3 70 2.5 3.9 0.622 2951 Example 23

INDUSTRIAL APPLICABILITY

The process for producing a polyester resin of the present inventionenables a polyester resin having good transparency, good color tone andhigh melt stability to be produced with high efficiency. All of thepolyester resins, polyester fibers, polyester films and polyesterbottle-formed articles of the present invention have good transparencyand color tone and can be produced in practice with high efficiency.

1. A process for producing a poly(ethylene aromatic carboxylate ester)resin comprising polycondensing a diester of an aromatic dicarboxylicacid with ethylene glycol in the presence of a catalyst system, whereinthe catalyst system comprises at least one member selected from thegroup consisting of: non-reacted mixtures and reaction products of (1) atitanium compound component comprising at least one member selected fromthe group consisting of titanium alkoxides and reaction products oftitanium alkoxides with aromatic polyvalent carboxylic acids oranhydrides thereof with (2a) a phosphorus compound component comprisingat least one member selected from the compounds represented by thegeneral formula (1):

wherein R¹, R² and R³ respectively and independently from each otherrepresent an alkyl group having 1 to 4 carbon atoms and X represents a—CH₂— group or a group represented by the formula (1a):

the catalyst system satisfying the requirements (a), (b) and (c):2≦M_(Ti)≦15  (a)1≦(M_(p)/M_(Ti))≦15  (b)10≦(M_(Ti)+M_(p))≦100  (c) in which requirements (a), (b) and (c),M_(Ti) represents a ratio of the amount in the units of milli moles oftitanium element contained in the catalyst system to the total amount inthe units of moles of the repeating ethylene aromatic dicarboxylateester units in the poly(ethylene aromatic dicarboxylate ester), M_(p)represents a ratio of the amount of phosphorus element in the units ofmilli moles contained in the catalyst system to the total amount in theunits of moles of the repeating ethylene aromatic dicarboxylate esterunits in the poly(ethylene aromatic dicarboxylate ester).
 2. The processfor producing a poly(ethylene aromatic dicarboxylate ester) resin asclaimed in claim 1, further comprising producing the diester of thearomatic dicarboxylic acid with ethylene glycol by a diesterificationreaction of the aromatic dicarboxylic acid with ethylene glycol.
 3. Theprocess for producing a poly(ethylene aromatic dicarboxylate ester)resin as claimed in claim 1, further comprising producing the diester ofan aromatic dicarboxylic acid with ethylene glycol by atransesterification reaction of a dialkylester of an aromaticdicarboxylic acid with ethylene glycol.
 4. The process for producing apoly(ethylene aromatic dicarboxylate ester) resin as claimed in claim 3,wherein the transesterification reaction of the dialkylester of thearomatic dicarboxylic acid with ethylene glycol is carried out in thepresence of at least the non-reacted or reacted titanium compoundcomponent (1); and the resultant reaction mixture from thetransesterification reaction and containing the diester of the aromaticdicarboxylic acid with ethylene glycol is subjected to apolycondensation reaction in the presence of a catalyst systemcomprising, together with at least the non-reacted or reacted titaniumcompound component (1) contained in the reaction mixture, thenon-reacted or reacted phosphorus compound component (2a).
 5. Theprocess for producing a poly(ethylene aromatic dicarboxylate ester)resin as claimed in any one of claims 1 to 4, wherein the aromaticdicarboxylic acid is selected from terephthalic acid, isophthalic acid,naphthalene dicarboxylic acid, 5-sulphoisophthalate metal salt and5-sulphoisophthalate onium salt.
 6. The process for producing apoly(ethylene aromatic dicarboxylate ester) resin as claimed in claim 3or 4, wherein the dialkylester of the aromatic dicarboxylic acid isselected from dimethyl terephthalate, dimethyl isophthalate dimethylnaphthalate, diethyl terephthalate, diethyl isophthalate and diethylnaphthalate.
 7. The process for producing a poly(ethylene aromaticdicarboxylate ester) resin as claimed in claim 1, wherein the titaniumalkoxides for the titanium compound component (1) are selected from thetitanium compounds represented by the general formula (4):

in which formula (4), R⁵, R⁶, R⁷ and R⁸ respectively and independentlyfrom each other represent an alkyl group having 2 to 10 carbon atoms ora phenyl group, and mc represents an integer of 1 to
 4. 8. The processfor producing a poly(ethylene aromatic dicarboxylate ester) resin asclaimed in claim 1, wherein the aromatic polyvalent carboxylic acids forthe titanium compound component (1) are selected from the compoundsrepresented by the general formula (5):

in which formula (5), na represents an integer of 2 to
 4. 9. The processfor producing a poly(ethylene aromatic dicarboxylate ester) resin asclaimed in claim 3, wherein the transesterification reaction is carriedout under a pressure of 0.05 to 0.20 MPa.
 10. The process for producinga poly(ethylene aromatic dicarboxylate ester) resin as claimed in claim3, wherein the dialkylester of the aromatic dicarboxylic acid to besubjected to the transesterification reaction comprises dimethylterephthalate in an amount of 80 molar % or more based on the totalmolar amount of the dialkylester of the aromatic dicarboxylic acid. 11.The process for producing a poly(ethylene aromatic dicarboxylate ester)resin as claimed in claim 3, wherein the dialkylester of the aromaticdicarboxylic acid to be subjected to the transesterification reactioncontains dialkyl terephthalate recovered by depolymerizing polyalkyleneterephthalate in an amount of 70 molar % or more based on the totalmolar amount of the dialkylester of the aromatic dicarboxylic acid. 12.The process for producing a poly(ethylene aromatic dicarboxylate ester)resin as claimed in claim 11, wherein the recovered dialkylterephthalate contains 2-hydroxyterephthalic acid in a contentcontrolled to 2 ppm or less.
 13. The process for producing apoly(ethylene aromatic dicarboxylate ester) resin as claimed in claim 4,wherein the catalyst system comprises a non-reacted mixture of thetitanium compound component (1) with the phosphorus compound component(2a); the whole amount of the titanium compound component (1) is addedinto the reaction system before or at the start of thetransesterification; and the whole amount of the phosphorus compoundcomponent (2a) is added into the resultant reaction system from thetransesterification reaction before or at the start of thepolycondensation reaction.
 14. The process for producing a poly(ethylenearomatic dicarboxylate ester) resin as claimed in claim 4, wherein thecatalyst system comprises a reaction product of the titanium compoundcomponent (1) with the phosphorus compound component (2a); the wholeamount of the catalyst system is added into the reaction system beforeor at the start of the transesterification reaction; and after thetransesterification reaction is completed, the resultant reactionmixture is subjected to the polycondensation reaction.
 15. The processfor producing a poly(ethylene aromatic dicarboxylate ester) resin asclaimed in claim 4, wherein before the transesterification reaction, aportion of the titanium compound component (1), or a portion thereaction product of the titanium compound component (1) with thephosphorus compound component (2a) is added into the reaction system,and at least one stage during and after the completion of thetransesterification reaction and before and during the polycondensationreaction, the remaining portion of the above-mentioned catalystcomponent is added into the reaction system.
 16. The process forproducing a poly(ethylene aromatic dicarboxylate ester) resin as claimedin claim 2, wherein the whole amount of the phosphorus compoundcomponent (2a) is added into the diesterification reaction system beforethe start of the diesterification reaction, or a portion of thephosphorus compound component (2a) is added into the diesterificationreaction system before the start of the reaction, and the remainingportion of the phosphorus compound component (2a) is added, at least onestage during and after the completion of the diesterification reactionand before the start of and during the polycondensation reaction, intothe reaction system.
 17. A poly(ethylene aromatic dicarboxylate ester)resin produced by the process as claimed in claim 1 for producing apoly(ethylene aromatic dicarboxylate ester) resin.
 18. The poly(ethylenearomatic dicarboxylate ester) resin as claimed in claim 17, furthercomprising an antioxidant hindered phenol compound in a content of 1% bymass or less.
 19. The process for producing a poly(ethylene aromaticdicarboxylate ester) resin as claimed in claim 1, wherein poly(ethylenearomatic dicarboxylate ester) resin contains antimony element andgermanium element each in a content controlled to 5/1000 molar % orless.
 20. Polyester fibers comprising a poly(ethylene aromaticdicarboxylate ester) resin as claimed in claim
 17. 21. The polyesterfibers as claimed in claim 20, wherein the poly(ethylene aromaticdicarboxylate ester) resin comprises, as a principal component,polyethylene terephthalate.
 22. A polyester film comprising apoly(ethylene aromatic dicarboxylate ester) resin as claimed in claim17.
 23. The polyester film as claimed in claim 22, wherein thepoly(ethylene aromatic dicarboxylate ester) resin comprises, as aprincipal component, polyethylene terephthalate.
 24. A bottle-formedpolyester article comprising a poly(ethylene aromatic dicarboxylateaster) resin as claimed in claim
 17. 25. The bottle-formed polyesterarticle as claimed in claim 24, wherein the poly(ethylene aromaticdicarboxylate ester) resin comprises, as a principal component,polyethylene terephthalate.